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Author Topic: Better IMD please  (Read 121773 times)
VE7RF
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Posts: 212




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« Reply #135 on: December 11, 2011, 05:57:58 AM »

Jim,,,, I was talking about ON FREQUENCY AUDIO quality not wide band  off channel IMD products. Are you saying when you switch too class A bias on Yaesu that you can hear a difference in on channel transmit audio quality from miles away?

This is also the reason why we need regulations. When you have operators who have a arrogant   and non technical approach as to how they operate their equipment without due regard to  the harm it does to other peoples ability to enjoy the hobby, its then time to act with regulation.
Hams get their license from the Cheerios box these days, and very few have the understanding  of a complex things like PA's. Just ask many hams what the IMD specifications of their transmitters and amplifiers are, when you get the answer you will understand why we need regulations. I have heard so many hams with Yaesu Class A radios asking their friends to check their audio quality after they switch it into ClassA. Its staggering that hams  think that the Class A bias on a radio has got something to do with audio quality.

###  whoa!  A bunch of us were on 80m, at midnight, and all using ESSB. One of the fellow's toggled between class A and class AB.... and I could just hear the difference from 1300 miles away. That surprised me. It's def cleaner.  The inband IMD drops like a rock.  Off freq, it's blatantly obvious. Remember your 2 x tones tests?  If the tones are say 200 hz apart, then all your odd order products, like 3-5-7-9 etc, will also be all 200 hz apart...and they will all be INband.  


Yeah! you're probably right.  But, not too many hams build their own equipment these days.  When is the last time you heard someone running a homebrew radio?  There are people out there building their own amps but they are a diminishing population.

###  That's nonsense.  There are more HB tube amps being built these days than ever before.  There are loads more vac tune and load caps available, and ditto with HV caps, and surplus tubes like YC-156's, 8877's pulled from MRI machines etc. You can find anything on the internet. It's easier now, than it ever was back in the 70's.  A smile comes across  my face when I know I just beat Alpha, et all, at their own game. If you want to spend $7k on a 1.5 kw amp, go ahead on it. 1/4", 3/8" and 1/2" copper tubing is dirt cheap at home depot down the street. I silver plate all mine with that cool-amp glop . Toss in the ceramic vac tune and load caps, and the manually tuned, tuned inputs, digital readout turns counters, humongous dahl plate xfmr's, ceramic vac relays on the input, output, and bias, plus some real connector's ,like 7-16 Din, then it's a winner.  I just got in a few 10-1000pf @ 15 kv ceramic, motor driven jennings vac caps...and the mating 35-4000pf @ 5/10 kv ceramic vac caps.  A GG triode amp is pretty simple stuff, no rocket science.   My 3CX-3000A7  has -59db pep  IMD-3, and the tube is rebuildable. The 225 watt CCS grid can be used as a dummy load for a FT-1000D.

Later...Jim  VE7RF



##  Yes, I mean ON freq. 8 x folks on freq, and only myself and one other could hear when he switched between A/AB.    The other fellow that could also hear the diff, is a broadcast eng.  [When I do the same a/ab toggling, I can barely tell the difference, on freq..while listening to myself on a 2nd RX.]  You can tell there is something sounding different in there.  That was with 100-5600 hz TX audio..and at both ends. This may be a case of BW, dunno .  Off freq, it's like apples and oranges.

Jim  VE7RF
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M0HCN
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« Reply #136 on: December 11, 2011, 08:44:27 AM »

ZENKI, you need to read that datasheet more carefully.....

It is VHF porn, but NXP are ONLY characterizing that part at 225Mhz, no idea how it would behave on HF.
Also, it is a 500Mhz part, so stability will be a can of worms. 

Finally, note the 0.23 C/W package thermal resistance, @ 400W dis, that equates to 92 degrees C between the die and the heatsink, so limiting you to about 50 degrees maximum heatsink mating surface temp, good luck with that.

The 70% efficiency figure can only possibly apply to deeply saturated class C, no way will it do that in linear service.

I would second the observation that there is no need for anything magic to improve the performance of most of the stuff out there by 10 -15dB or so, I am playing with doing much better by using advanced techniques because I am interested in them, not because they are needed to do much better then a lot of the stuff out there. 

Regards, Dan.
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W4VR
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Posts: 1214


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« Reply #137 on: December 11, 2011, 09:17:18 AM »

Jim,,,, I was talking about ON FREQUENCY AUDIO quality not wide band  off channel IMD products. Are you saying when you switch too class A bias on Yaesu that you can hear a difference in on channel transmit audio quality from miles away?

This is also the reason why we need regulations. When you have operators who have a arrogant   and non technical approach as to how they operate their equipment without due regard to  the harm it does to other peoples ability to enjoy the hobby, its then time to act with regulation.
Hams get their license from the Cheerios box these days, and very few have the understanding  of a complex things like PA's. Just ask many hams what the IMD specifications of their transmitters and amplifiers are, when you get the answer you will understand why we need regulations. I have heard so many hams with Yaesu Class A radios asking their friends to check their audio quality after they switch it into ClassA. Its staggering that hams  think that the Class A bias on a radio has got something to do with audio quality.

###  whoa!  A bunch of us were on 80m, at midnight, and all using ESSB. One of the fellow's toggled between class A and class AB.... and I could just hear the difference from 1300 miles away. That surprised me. It's def cleaner.  The inband IMD drops like a rock.  Off freq, it's blatantly obvious. Remember your 2 x tones tests?  If the tones are say 200 hz apart, then all your odd order products, like 3-5-7-9 etc, will also be all 200 hz apart...and they will all be INband.  


Yeah! you're probably right.  But, not too many hams build their own equipment these days.  When is the last time you heard someone running a homebrew radio?  There are people out there building their own amps but they are a diminishing population.

###  That's nonsense.  There are more HB tube amps being built these days than ever before.  There are loads more vac tune and load caps available, and ditto with HV caps, and surplus tubes like YC-156's, 8877's pulled from MRI machines etc. You can find anything on the internet. It's easier now, than it ever was back in the 70's.  A smile comes across  my face when I know I just beat Alpha, et all, at their own game. If you want to spend $7k on a 1.5 kw amp, go ahead on it. 1/4", 3/8" and 1/2" copper tubing is dirt cheap at home depot down the street. I silver plate all mine with that cool-amp glop . Toss in the ceramic vac tune and load caps, and the manually tuned, tuned inputs, digital readout turns counters, humongous dahl plate xfmr's, ceramic vac relays on the input, output, and bias, plus some real connector's ,like 7-16 Din, then it's a winner.  I just got in a few 10-1000pf @ 15 kv ceramic, motor driven jennings vac caps...and the mating 35-4000pf @ 5/10 kv ceramic vac caps.  A GG triode amp is pretty simple stuff, no rocket science.   My 3CX-3000A7  has -59db pep  IMD-3, and the tube is rebuildable. The 225 watt CCS grid can be used as a dummy load for a FT-1000D.

Later...Jim  VE7RF



##  Yes, I mean ON freq. 8 x folks on freq, and only myself and one other could hear when he switched between A/AB.    The other fellow that could also hear the diff, is a broadcast eng.  [When I do the same a/ab toggling, I can barely tell the difference, on freq..while listening to myself on a 2nd RX.]  You can tell there is something sounding different in there.  That was with 100-5600 hz TX audio..and at both ends. This may be a case of BW, dunno .  Off freq, it's like apples and oranges.

Jim  VE7RF

By diminishing population I meant the old timers are pushing daisies and most younger hams don't have a clue on how to build an amplifier.  I used to build my own amplifiers when I was young and poor, but now that I am better equipped financially I buy them.
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GM3SEK
Member

Posts: 99




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« Reply #138 on: December 12, 2011, 12:57:51 AM »


By diminishing population I meant the old timers are pushing daisies and most younger hams don't have a clue on how to build an amplifier.  I used to build my own amplifiers when I was young and poor, but now that I am better equipped financially I buy them.

The difference is that OT's who used to build amplifiers bring all that experience with them, and have now become very demanding consumers instead.

In this discussion, please let's keep our focus on the amplifiers that are inside our transceivers where there is much less choice between 'build or buy'. We know there is also a separate issue of IMD in external amplifiers, and integration issues between the two; but first, please, the transceiver.

Regarding the FT-767 and its good TX IMD performance, this may have been due to its age. It would have been designed just before the manufacturers switched their best engineers to work on the problems of RX IMD. Ever since then, it seems like transmitter design has been left to junior engineers. Extra money that has been spent on the RX has been clawed back from the TX design, especially those elments of over-design that are so important to IMD... and so the TX performance has been allowed to slide.

The extra spending on RX performance was driven almost entirely by equipment reviews; but if reviewers wish to take any credit for that, they must also share the blame for allowing the slide in TX performance.

The big national societies - ARRL, RSGB and DARC - publish these reviews as a service to their members. What they forget is that, when one person buys a transceiver on the basis of a good review, there will be hundreds more of us who have to listen to the darn thing!


73 from Ian GM3SEK

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ZENKI
Member

Posts: 1648




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« Reply #139 on: December 12, 2011, 01:04:42 AM »

Dan

You might be right. However in my experience any device which has superior IMD at a higher frequency will in all probability have better IMD performance at a lower frequency. In some case the  IMD gets worst at the lower frequency limit. Well thats where real engineers come into the picture, they measure and test everything before drawing conclusions. Unlike  ham companies who copy each others bad PA design which was copied from an illegal CB amp. Just looking at these PA's tells you lot about their design heritage!

Dan I look forward to the day when you publish your experiments and data in QEX.

The ARRL had a competition for hams who could build the cheapest amplifier. Maybe one day they will have a competition for the worlds cleanest  and cheapest amplifier. You should be able to take first prize.  I doubt however that the ARRL is interested in highlighting a issue that will  make their advertised products look bad.



ZENKI, you need to read that datasheet more carefully.....

It is VHF porn, but NXP are ONLY characterizing that part at 225Mhz, no idea how it would behave on HF.
Also, it is a 500Mhz part, so stability will be a can of worms. 

Finally, note the 0.23 C/W package thermal resistance, @ 400W dis, that equates to 92 degrees C between the die and the heatsink, so limiting you to about 50 degrees maximum heatsink mating surface temp, good luck with that.

The 70% efficiency figure can only possibly apply to deeply saturated class C, no way will it do that in linear service.

I would second the observation that there is no need for anything magic to improve the performance of most of the stuff out there by 10 -15dB or so, I am playing with doing much better by using advanced techniques because I am interested in them, not because they are needed to do much better then a lot of the stuff out there. 

Regards, Dan.
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ZENKI
Member

Posts: 1648




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« Reply #140 on: December 12, 2011, 01:16:45 AM »

OK, Jim  I have a MK5  I will try it and listen to Class A bias using a 12khz filter in the SDR  while switching between class A and AB. Maybe you should ask your buddy to say that he is switching and he does not switch between the class A bias and class AB. I used to do that when testing between a quad and yagi,  on the many occasions that people reported a big difference in favor of the quad I had not switch at all! The quad was their emotional favorite. When I operated from EA8 land, I did the same thing with a G5RV.  I was comparing a G5RV to all band open wire fed delta loop. Just about everyone said the G5RV was bad, when I called the G5RV  a double extended zepp, everyone said that the Zepp was better!
Many hams have an over active imagination. Its like the hams who says your amplifier made 20db of difference and their tone of voice implies that they speaking with authority and that their equipment calibrated by NIST! When I say the difference should be 6db they say mine says 20db! Can you trust anyone these days? Its just as bad asking your friend if you are splattering, friends never want to offend friends and call a spade a spade. Thats how ham radio is today!
[/quote]
[/quote]
[/quote]

##  Yes, I mean ON freq. 8 x folks on freq, and only myself and one other could hear when he switched between A/AB.    The other fellow that could also hear the diff, is a broadcast eng.  [When I do the same a/ab toggling, I can barely tell the difference, on freq..while listening to myself on a 2nd RX.]  You can tell there is something sounding different in there.  That was with 100-5600 hz TX audio..and at both ends. This may be a case of BW, dunno .  Off freq, it's like apples and oranges.

Jim  VE7RF
[/quote]
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VE7RF
Member

Posts: 212




Ignore
« Reply #141 on: December 12, 2011, 05:35:28 AM »


By diminishing population I meant the old timers are pushing daisies and most younger hams don't have a clue on how to build an amplifier.  I used to build my own amplifiers when I was young and poor, but now that I am better equipped financially I buy them.

The difference is that OT's who used to build amplifiers bring all that experience with them, and have now become very demanding consumers instead.

In this discussion, please let's keep our focus on the amplifiers that are inside our transceivers where there is much less choice between 'build or buy'. We know there is also a separate issue of IMD in external amplifiers, and integration issues between the two; but first, please, the transceiver.

Regarding the FT-767 and its good TX IMD performance, this may have been due to its age. It would have been designed just before the manufacturers switched their best engineers to work on the problems of RX IMD. Ever since then, it seems like transmitter design has been left to junior engineers. Extra money that has been spent on the RX has been clawed back from the TX design, especially those elments of over-design that are so important to IMD... and so the TX performance has been allowed to slide.

The extra spending on RX performance was driven almost entirely by equipment reviews; but if reviewers wish to take any credit for that, they must also share the blame for allowing the slide in TX performance.

The big national societies - ARRL, RSGB and DARC - publish these reviews as a service to their members. What they forget is that, when one person buys a transceiver on the basis of a good review, there will be hundreds more of us who have to listen to the darn thing!


73 from Ian GM3SEK



## IMO, the QST reviews have gone way down hill, ever since they stopped doing the extended lab reports.  Heck, they don't even do the all important IN band RX IMD tests anymore [ 200 hz spacing. They did it at Both S-9 and also 60 over S-9..and also with agc on fast, then again on slow, the results are a real eye opener]. The TX imd test are over simplified too. No more SA pix.At least with the extended lab report, on my MK-V, you got a IMD chart for EVERY band..and in both Class AB..then repeat it all again for class A. They should have also done the TX imd tests at several different power levels in class AB mode.  It's fine to say the worse band for  TX IMD is 12m, [and at 200w pep out], but I don't operate 12m. I also don't require 200w pep to drive my 2 x 3-500Z amp either.  The MK-V is a blast furnace on class A, and it's only 75w pep out anyway, so I can't use it in class A. 

## The  100w pep 767GX uses the same pair of MRF-422's as my  200w pep FT-1000-D. The 1000-D sucks 1000 ma on idle [500ma per device].  I don't think this is a case of bad IMD as it is having all these new xcvr's being 200w pep output rigs.  I had a serious look at the yaesu 9000-MP [400w version], but the unit they tested had lousy imd on both 10+12m [-22db pep]. It was also -22db pep on 80m. [16db below one tone]. I'd be run outa town with -22db pep imd.  On the other bands, it was good, like -36db pep.  OK, what is it with just 200W pep out ?   It may well improve to -40db pep. Who knows?  I'm not about to drop $12K just to find out either. I'm tired of being the guinea pig. I need a clean 200w pep out, to drive the 3CX-3000A7. I bought the 1000-D and also the MK-V on the premise that to get a clean sounding 100w xcvr, you buy a 200w xcvr, then run it at half power, but that was b4 the 3x3 amp came along. 

##  I can tune across 80m..and pick out every Icom 756 pro2+3 and also the 7800 by ear. My brooadcast eng ham buddy sez it's imd. I say it's digital artifact grunge. They all have a distinct sonic footprint. I can hear all sorts of crap on them on the opposite sideband too.

Later...Jim VE7RF
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VE7RF
Member

Posts: 212




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« Reply #142 on: December 12, 2011, 06:21:01 AM »

OK, Jim  I have a MK5  I will try it and listen to Class A bias using a 12khz filter in the SDR  while switching between class A and AB. Maybe you should ask your buddy to say that he is switching and he does not switch between the class A bias and class AB. I used to do that when testing between a quad and yagi,  on the many occasions that people reported a big difference in favor of the quad I had not switch at all! The quad was their emotional favorite. When I operated from EA8 land, I did the same thing with a G5RV.  I was comparing a G5RV to all band open wire fed delta loop. Just about everyone said the G5RV was bad, when I called the G5RV  a double extended zepp, everyone said that the Zepp was better!
Many hams have an over active imagination. Its like the hams who says your amplifier made 20db of difference and their tone of voice implies that they speaking with authority and that their equipment calibrated by NIST! When I say the difference should be 6db they say mine says 20db! Can you trust anyone these days? Its just as bad asking your friend if you are splattering, friends never want to offend friends and call a spade a spade. Thats how ham radio is today!
[/quote]
[/quote]

##  Yes, I mean ON freq. 8 x folks on freq, and only myself and one other could hear when he switched between A/AB.    The other fellow that could also hear the diff, is a broadcast eng.  [When I do the same a/ab toggling, I can barely tell the difference, on freq..while listening to myself on a 2nd RX.]  You can tell there is something sounding different in there.  That was with 100-5600 hz TX audio..and at both ends. This may be a case of BW, dunno .  Off freq, it's like apples and oranges.

Jim  VE7RF
[/quote]
[/quote]

##  I hear you. I call it as I see it. I'm no BS artist.  I think I still have the recordings on mini disc too. I have a rack mount sony mini disc machine for RX. The fellow toggling between Class A and AB was also using a modified MK-V, same as mine. We have both modified the crap out of them, and were listening to each other using 5.7 khz RX.RX audio was tapped off the analog product detector..and then fed externally.  [ he was using 4.3 khz TX BW that night]. The band was lousy that night too, noisy, and signals way down from normal.  A week later, then the band was good, I couldn't hear any diff at all, yet other's in the LA area sure could. 

On a similar note, I spent months tweaking my digital reverb, [ 32 x things to adjust, 2 million combo's]..and found a combo that improved the copy when the band was lousy, and typ 80m summer time static crashes etc.  I ran hundreds of tests with KCOXX over 2 x summer's and he's not much above my noise level at the best of times. When it was real bad, he swears the copy at his end goes from Q3 to Q5.  The theory is, the transients etc, get stretched, so they are perceived as being louder under some condx. That's using reverb tails that are only  a few msec long. I split the TX audio into 3x bands inside the reverb, and tweak each band slightly differently.

##  One thing that is very  blatantly obvious is when the top end is  extended out to at least 3600hz, it's real easy to copy each other. With 3900 hz and higher, no need to use phonetics ever again, even under weak signal condx.  The consonants don't get "crushed". I ended up re-inventing the wheel, since it had all been done before, and explained in great detail..in "SSB, systems and circuits", written by collins engineers. They even ran the BW tests using random word groups+ normal word groups. They chopped the bottom end off at 200hz...and kept extending the top end out...up to 6100hz.  The inteligence recovery goes WAY up when the top end BW gets extended.  They have loads of charts showing the results.  Now this all works provided no QRM.  Also, I need real  low TX imd when using wider BW SSB.

later...Jim  VE7RF
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W4VR
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« Reply #143 on: December 12, 2011, 08:50:16 AM »


"I can tune across 80m..and pick out every Icom 756 pro2+3 and also the 7800 by ear. My brooadcast eng ham buddy sez it's imd. I say it's digital artifact grunge. They all have a distinct sonic footprint. I can hear all sorts of crap on them on the opposite sideband too. VE7RF"

Don't know about the 7800, but the PRO series, including the 7600, have terrible IMD and poor opposite sideband suppressions..could also be some digital artifact.  I have the 7600 and sometimes get reports of either being too wide or poor suppression on the upper.  I did my own IMD two-tone tests on several bands with and without the PW-1, and it's OK but not terrific.  The people that normally complain are those that say I'm 40 over 9 on a quiet 17 meter band.  Some of this may also be related to receiver IMD, but who knows.  Most folks don't mind complaining about transmitter issues, but if you tell them their receivers may be as much to blame they get upset.  If you want to hear broad signals listen to those SDR radios....they tend to open them up too wide.
 













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VE7RF
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« Reply #144 on: December 12, 2011, 09:18:38 AM »


"I can tune across 80m..and pick out every Icom 756 pro2+3 and also the 7800 by ear. My brooadcast eng ham buddy sez it's imd. I say it's digital artifact grunge. They all have a distinct sonic footprint. I can hear all sorts of crap on them on the opposite sideband too. VE7RF"

Don't know about the 7800, but the PRO series, including the 7600, have terrible IMD and poor opposite sideband suppressions..could also be some digital artifact.  I have the 7600 and sometimes get reports of either being too wide or poor suppression on the upper.  I did my own IMD two-tone tests on several bands with and without the PW-1, and it's OK but not terrific.  The people that normally complain are those that say I'm 40 over 9 on a quiet 17 meter band.  Some of this may also be related to receiver IMD, but who knows.  Most folks don't mind complaining about transmitter issues, but if you tell them their receivers may be as much to blame they get upset.  If you want to hear broad signals listen to those SDR radios....they tend to open them up too wide.
 



## I can pluck them out like flys.  And that's using the 1000-d and also the MK-V for RX.  Both main and sub rx.  That's S-7 to 20 over S-9 signals on a noisy 80m band. ..and also during the summer time static crashes, etc. Now check this out..from rob sherwood himself..hope he doesn't mind...later...Jim  VE7RF

...


If someone is saying a signal is X kHz wide, it all comes down to at how many dB
down are we speaking?

The K3 is about 7 kHz wide at -45 dB down, when tested with white noise feeding
the transmitter. This of course includes the normal transmit passband of about
2.7 or 2.8 kHz at -6 dB. So this is edge to edge at the -45 dB point.
My Pro III is about 8 kHz wide at -45 dB using the same white noise modulation.
The IC-7410 is about 10 kHz wide at -45 dB.
The IC-7600 is about 10 kHz wide at -45 dB.
The T-T Eagle is about 8 kHz wide at -45 dB.
The Yaesu FT-1000 Mk V is about 4 kHz wide at -45 dB when run in class A.
The FTdx-5000D in class A is about 3.5 kHz wide at -45 dB in class A with NO
ALC.
The FTdx-5000D in class A with ALC reading half scale (3 dB of ALC) is about 7
kHz wide.
So in the case of the 5000D, it is wonderful until you hit the ALC, and it
degrades to what one would get in class B.
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W4VR
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« Reply #145 on: December 12, 2011, 12:50:03 PM »

VE7RF: thanks for the Sherwood info.  It is disappointing, to say the least, to see how Icom has gone down the drain with respect to unwanted emissions management.  And I know for a fact that after numerous hams complained to Icom about the problem with the 7600 they would not listen...almost as if a fix is beyond their control.  When I did the transmit intermod tests on the 7600 and PROIII the results were about the same on both radios and very close to what ARRL found on these two radios in their product reviews.  Over the years I've complained to Icom about a LV supply issue in the PW-1; finally their supplier made a mod in the later serial numbered amps that supposedly fixed the problem.  But, Icom never admitted to me that there was a problem when I was telling them about it via email.  Oh, how I wish I would have kept my FT1000D and Alpha 89.  W4VR
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VK4DD
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« Reply #146 on: December 13, 2011, 01:36:50 AM »


If someone is saying a signal is X kHz wide, it all comes down to at how many dB
down are we speaking?

The K3 is about 7 kHz wide at -45 dB down, when tested with white noise feeding
the transmitter. This of course includes the normal transmit passband of about
2.7 or 2.8 kHz at -6 dB. So this is edge to edge at the -45 dB point.
My Pro III is about 8 kHz wide at -45 dB using the same white noise modulation.
The IC-7410 is about 10 kHz wide at -45 dB.
The IC-7600 is about 10 kHz wide at -45 dB.
The T-T Eagle is about 8 kHz wide at -45 dB.
The Yaesu FT-1000 Mk V is about 4 kHz wide at -45 dB when run in class A.
The FTdx-5000D in class A is about 3.5 kHz wide at -45 dB in class A with NO
ALC.
The FTdx-5000D in class A with ALC reading half scale (3 dB of ALC) is about 7
kHz wide.
So in the case of the 5000D, it is wonderful until you hit the ALC, and it
degrades to what one would get in class B.


Interesting numbers, but what band, what ALC action, what filter settings, what audio settings, what output level.

I can see that the FT1000D is better, I can see that the FT5000 in class A does well and might have some ALC issues which probably can be fixed in a software upgrade. Perhaps it is already fixed because this radio had some very good software upgrades.

I suppose bad ALC action can make the radio wide, but bad amplifier also.
May be the K3 has made the ALC better so that bad IM3 from the amplifier is not so noticeable.

On 2m using the internal transverter from the K3 the audio sounded so bad, that you did not know when you tuned zero beat. Funny audio bad IM3. First I removed the final transistor which was only 4 cm away from the local oscillator (heaps of drift which was corrected with a temperature sensitive resistor and a varicap). That had heaps of issues and a solution was found by elecraft to lock it with a 10 Mhz reference. I simply removed the NTC and put a heater on the Xtal. An external Mitsubishi module was choosen and IMD reached 40dBc.
A whopping 25dB better than the orignal.

Any way the whole discussion started to annoy me and I don't like to knock on the elecraft door and beg for a solution. So I started to look into it and come up with a plan.

I have purchased some BLF145 and some hybrid modules from Motorola.
These have flat gain from 1 to 200 Mhz with in 1 dB over that freq range and typically within 0.5dB between 1 to 50 MHz. May be I will use the BLF145 in push pull, may be single ended.
I got some inspiration for this solution when I looked at AN779 from Motorola.
Problem with these old application notes is that you can't buy these parts any more.
Please don't search for these parts, most is fake. Don't look on big auction sites this is a big gamble there is heaps of imitation around. In some countries they will stamp it with anything.
At 300mW out these cable amplifiers (thats how these hybrids are called) they have an IMD of around =50dBc to -60dBc. After that the linear BLF145 and bingo a clean signal.
Any way thats the theory any way. I have ordered some parts and time will tell if it works.

73 Ron.



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TANAKASAN
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Posts: 933




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« Reply #147 on: December 13, 2011, 03:58:06 AM »

If you want to see it done right have a look at http://www.eandiltd.com/RFAmplifier/A150.html

150 Watts Class A from 300 KHz to 35 MHz with a nice low IMD figure. The bad news, it weighs 48 lbs and it might break the bank.

Tanakasan
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VE7RF
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Posts: 212




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« Reply #148 on: December 13, 2011, 06:37:37 AM »

If you want to see it done right have a look at http://www.eandiltd.com/RFAmplifier/A150.html

150 Watts Class A from 300 KHz to 35 MHz with a nice low IMD figure. The bad news, it weighs 48 lbs and it might break the bank.

Tanakasan

##  nah, HERE is the real ticket      http://www.eandiltd.com/RFAmplifier/a1000
This is what I need.  Then you can drive the crap outa anything made.  Lottery tickets any one?  Actually, if u combined 2-10 of these cabinets... u would have the ultimate set up. Dunno if these include any form of LP filter or not. They are really  for lab/medical use.


## actually, they would be ideally suited for  ZENKI !  He could take it..and reduce the power to say 1/2..and get even better TX IMD.  His signal would then be so clean..and narrow, that the brain dead contesters would then snuggle up on both sides of him..so you still can't win.

Later... Jim  VE7RF
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N3OX
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« Reply #149 on: December 13, 2011, 06:41:17 AM »

## actually, they would be ideally suited for  ZENKI !  He could take it..and reduce the power to say 1/2..and get even better TX IMD.  His signal would then be so clean..and narrow, that the brain dead contesters would then snuggle up on both sides of him..so you still can't win.

That's why you need a "splatter" button that cuts you back to class C.

You know these people who run really lossy 75m antennas and gush about how "quiet" they are... these people are in severe need of a lesson on how to use the attenuator button with a high efficiency dipole.  You don't want to ALWAYS have to have your attenuator switched in, especially on TRANSMIT.

Same for excessive IMD for contesting ... you don't want it on ALL the time, just some of the time Grin
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
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