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Author Topic: Better IMD please  (Read 121779 times)
VE7RF
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Posts: 212




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« Reply #195 on: December 27, 2011, 12:46:04 AM »

The latest QST has a review of a TE 2M brick and they give it a -17dB 3rd and barely comment its not as good as they would like to see. The other ones aren't much better.
Jeez, how can they even accept advertising for that crap?? No conscience required when money crosses hands in ad revenue.

Carl

##  -17db pep.  Now that's  only -11 db  below one tone.   Now that is 4 x steps below crap. Seems to me most of these 2M brick amps are like this?   I have a small Mirage B310g...which has been around for eons,  but finally got into a qst review.  No mention of TX-IMD on ssb at all.  But they did mention that the FM/SSB  switch is to simply add .5 sec delay on ssb mode, when using the rf actuated  t/r relay.  I'm not 2m brick expert,  but it seems to me most of em are used for 2M FM.  That being the case, they probably bias em for class C...so the eff is good, and it minimizes temp on the heat sink.   Of course the imd will suck on SSB.  They could have easily installed a  DPDT switch, and used 1/2 of it to add the .5 sec delay, and the other 1/2 of the same switch to change the bias to linear class AB mode. 


## Later... Jim  VE7RF
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VE7RF
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Posts: 212




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« Reply #196 on: December 27, 2011, 01:46:14 AM »

We will get change when magazines such as QST start naming and shaming the poor transmitters. I don't hold much hope that the ARRL will actually use the words "poor IMD performance" in any review.

Although ARRL reviews may not comment on transmitter IMD in the text, IMD3 and IMD9 are prominently included in the the 'Key Performance Features' sidebar on the first page. The positions of the markers on bars shaded green-yellow-red must represent some kind of technical judgement on a scale 'from good to bad' (eg IMD3 of -29dBPEP is in the yellow zone).

Is there any published information about these shaded bars, and what judgements they represent?


73 from Ian GM3SEK

## The arrl 2 tone test is flawed anyway. It's db below pep, and not below one tone... and it does not dynamically test the various pwr supplies, and bias supplies, etc.  Providing just IMD3  and IMD9 is not good enough imo.  Why not at least go back to the old way..and give us a pix of the SA used for the test ?   IE: when arrl tested the 767GX, and other xcvr's, the SA clearly showed IMD-3 right up through IMD-21. That can easily be done with narrow spaced tones like 200hz.   Then one can easily tell at a glance if the IMD products fall off at a given rate...or do they keep going on and on and on forever.  The sidebar method is obscure and convoluted for a lot of stuff.  It might show "-40db"  at the extreme right side...then you find out that's the upper end of the scale, and not the actual number achieved.

##  and if any amp tests at -17db pep, it should be slammed, and good and hard, with a ... "we strongly do NOT recommend this product, due  to it's interference potential "   And then refuse to accept their ads. Anything advertised in QST is supposed to meet specs and certain criteria.  If you accept advertising $$ from these idiots, and folks read the ads, but miss the qst reviews, then joe ham buys this junk..and the result is an obvious mess on the band involved. What is the arrl gonna do then, tell folks to buy something else ?  Too late then, thousands of junk amplifiers have then been sold. What's Plan B...yet another..."band plan" ? 

## Even with IMD quoted, most hams will not know whether -30db is good or not.  Something to the effect of..."-40db pep  for IMD-3  is suggested, with higher order products even lower still".

## as is, QST/arrl keeps on promoting junk radio's.  The junk does not get a bad rap in the review [ they had their chance and golden opportunity... and blew it].  Instead, it ends up in the ads sections, as a 1/2 or full page display.   I say blame the various magazines.  What they should be doing is... 'sorry,we can not accept your model XXX amplifier  for advertising in our esteemed publication, due to it not meeting our suggested MINIMUM tech standards.

##  any review is a one shot deal. You get just ONE chance to do it right.

Later... Jim  VE7RF
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ZENKI
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Posts: 1648




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« Reply #197 on: December 27, 2011, 04:27:16 AM »

I agree with your comments.  The ARRL only listens to itself , very few outsiders have had much luck changing the way they do things.

The old expanded test reports were very useful and you get to see the full IMD test for all bands at different power levels. It was easy spotting a bad  radio like the TS870S which had  very lousy IMD performance on the higher bands. Then again people who bought that radio hardly bothered reading the data.   

I dont think I will ever see the ARRL make any adverse findings in print against any of their advertisers, thats just  how the world works! The German reviews tend to call a spade a spade and will comment when  the IMD is bad or if the receiver has bad RX IMD etc  What good does this really do at the end of the day when we dont have a standard thats legally enforceable by law. Its almost pointless even doing a IMD test if there is no mandated standard.

Failing legal standards would be cause for concern. You often see this in the ARRL reviews when a radio fails spurious harmonic standards. The ARRL is  quick to contact the manufacturer and ask whats going on. In most cases its a faulty radio that needs updates. Why cant we have this kind of regime for TX IMD? If the IMD performance is lousy it should go back to the factory to be fixed not put on the shelves. This wont happen unless IMD testing is made a mandatory requirement by the FCC as part of their Type Acceptance test regime.

 A lot of people forget that many of the FCC laws and standards are exactly the same laws as the  ITU. The US is a signatory to enforcing  global International ITU standards. It would be a  1 line change in the amateur type acceptance laws for IMD standards to be made mandatory. Ickensu would just go along  they would not oppose such changes in the law. All the naysayers will be surprised at how quickly they will change the designs of the transmitters when they are forced to do so.

[/quote]

## The arrl 2 tone test is flawed anyway. It's db below pep, and not below one tone... and it does not dynamically test the various pwr supplies, and bias supplies, etc.  Providing just IMD3  and IMD9 is not good enough imo.  Why not at least go back to the old way..and give us a pix of the SA used for the test ?   IE: when arrl tested the 767GX, and other xcvr's, the SA clearly showed IMD-3 right up through IMD-21. That can easily be done with narrow spaced tones like 200hz.   Then one can easily tell at a glance if the IMD products fall off at a given rate...or do they keep going on and on and on forever.  The sidebar method is obscure and convoluted for a lot of stuff.  It might show "-40db"  at the extreme right side...then you find out that's the upper end of the scale, and not the actual number achieved.

##  and if any amp tests at -17db pep, it should be slammed, and good and hard, with a ... "we strongly do NOT recommend this product, due  to it's interference potential "   And then refuse to accept their ads. Anything advertised in QST is supposed to meet specs and certain criteria.  If you accept advertising $$ from these idiots, and folks read the ads, but miss the qst reviews, then joe ham buys this junk..and the result is an obvious mess on the band involved. What is the arrl gonna do then, tell folks to buy something else ?  Too late then, thousands of junk amplifiers have then been sold. What's Plan B...yet another..."band plan" ? 

## Even with IMD quoted, most hams will not know whether -30db is good or not.  Something to the effect of..."-40db pep  for IMD-3  is suggested, with higher order products even lower still".

## as is, QST/arrl keeps on promoting junk radio's.  The junk does not get a bad rap in the review [ they had their chance and golden opportunity... and blew it].  Instead, it ends up in the ads sections, as a 1/2 or full page display.   I say blame the various magazines.  What they should be doing is... 'sorry,we can not accept your model XXX amplifier  for advertising in our esteemed publication, due to it not meeting our suggested MINIMUM tech standards.

##  any review is a one shot deal. You get just ONE chance to do it right.

Later... Jim  VE7RF
[/quote]
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VK4DD
Member

Posts: 79




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« Reply #198 on: December 27, 2011, 02:37:16 PM »

Zenki,

I don't know what to think. I see here a test from IK4AUY with an Amplfier from RM. Zenki has given this manufacturer a couple of tilles. But lets go to the facts. IMD -46dB on 20m (as per ARLL add 6dB amateur IM3 method). This exceeds the specs of just about any radio, including the FT5000 in class A. Cleaner than anything around. The CB amplifier manufacturer does a better job. I am speechless, I don't know what to think of this.

500W out from the RM1000 BLA / IM3 -46dBc on 20m !!

See:
Quote
BLA1000 two tones RF  IMD test  with a newly low IMD  RF coupler design by I4SBX
at 500W pep out      (with 2x15W  CW RF tones coupled or 30Wpep RF in)
IM3 -46dBc

http://ik4auy.xoom.it/hf_tetrode_lin_amp.htm

Apparently not all CB gear is bad and not all HAM gear is good.
But this RM1000 BLA does an excellent job with 500W out.
Keep in mind that is 3dB better than the FT5000 in class A.(the best rig money could buy as far as IM3).

If you comment, PLEASE stick to the facts, no unsubstantiated claims and don't confuse it with rubbish about their other products. Stick to the topic.

73 Ron
VK4DD

PS If this was a CB amp, than it would have had a different name.
Like CB5000 DX, claming 5000 Watts.
« Last Edit: December 27, 2011, 02:48:01 PM by VK4DD » Logged
ZENKI
Member

Posts: 1648




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« Reply #199 on: December 27, 2011, 04:44:46 PM »

So you going to pay 4000 dollars for a 1 kilowatt amplifier and run it at 500 watts?

If I wanted  a clean amplifier with -40db 3rd order and good high order suppression I would use a tube amp that uses a 8877 or 3cx800 tube. You can buy an Ameritron Al1500 for 2500 dollars and it is capable of 2.5kw output and  maintain its excellent IMD performance. Solid state amplifiers cannot match the IMD performance of good linear triodes. Even a pair  of 3-500's perform better than most solid state amplifiers.

Lets see what the IMD figures are at the rated output. Is it not cheating specifying your IMD products at half power output?   Show us the data at the rated output power of the amplifier.  Anyone can play the smoke and mirror games with 2 tone numbers. 



Zenki,

I don't know what to think. I see here a test from IK4AUY with an Amplfier from RM. Zenki has given this manufacturer a couple of tilles. But lets go to the facts. IMD -46dB on 20m (as per ARLL add 6dB amateur IM3 method). This exceeds the specs of just about any radio, including the FT5000 in class A. Cleaner than anything around. The CB amplifier manufacturer does a better job. I am speechless, I don't know what to think of this.

500W out from the RM1000 BLA / IM3 -46dBc on 20m !!

See:
Quote
BLA1000 two tones RF  IMD test  with a newly low IMD  RF coupler design by I4SBX
at 500W pep out      (with 2x15W  CW RF tones coupled or 30Wpep RF in)
IM3 -46dBc

http://ik4auy.xoom.it/hf_tetrode_lin_amp.htm

Apparently not all CB gear is bad and not all HAM gear is good.
But this RM1000 BLA does an excellent job with 500W out.
Keep in mind that is 3dB better than the FT5000 in class A.(the best rig money could buy as far as IM3).

If you comment, PLEASE stick to the facts, no unsubstantiated claims and don't confuse it with rubbish about their other products. Stick to the topic.

73 Ron
VK4DD

PS If this was a CB amp, than it would have had a different name.
Like CB5000 DX, claming 5000 Watts.
Logged
VK4DD
Member

Posts: 79




Ignore
« Reply #200 on: December 27, 2011, 08:02:59 PM »

So you going to pay 4000 dollars for a 1 kilowatt amplifier and run it at 500 watts?

If I wanted  a clean amplifier with -40db 3rd order and good high order suppression I would use a tube amp that uses a 8877 or 3cx800 tube. You can buy an Ameritron Al1500 for 2500 dollars and it is capable of 2.5kw output and  maintain its excellent IMD performance. Solid state amplifiers cannot match the IMD performance of good linear triodes. Even a pair  of 3-500's perform better than most solid state amplifiers.

Lets see what the IMD figures are at the rated output. Is it not cheating specifying your IMD products at half power output?   Show us the data at the rated output power of the amplifier.  Anyone can play the smoke and mirror games with 2 tone numbers.  


Dear Zenki,

You talk about "smoke and mirrors"?
You should not accuse some else if you do the same thing your self. You hide behind a smoke screen called Zenki.

As far as your comments. Generally no bad IM3 will be advertised, other wise manufacturers would not sell their gear, that is life.  Bill Gates once said
Quote
"Life is not fair, better get used to it"
.

Tubes vs Fets.
Fets are getting real good as far as IM3. Solite state is going through a revolution. Parts like the MRF150 /151 and alike are still the old generation solid state.
Much better is possible and we will hopefully see good products in the future. But what's the point if we have only one radio who can do it? the FT5000. Hopefully the other manufacturers can follow Yeasu?

Tubes: Who uses the 3cx800 or the 8877 these days, they are all replaced for lower cost tubes. Its a pity that a real good american product is replaced. But hams vote with their wallets and I do understand that not everybody has got a credit card with Bill Gates on it.

Zenki, if you want to accomplish something do it with dignity and post under your call sign.

73 Ron
VK4DD
« Last Edit: December 27, 2011, 11:19:00 PM by VK4DD » Logged
VE7RF
Member

Posts: 212




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« Reply #201 on: December 28, 2011, 08:33:11 AM »

Zenki,

I don't know what to think. I see here a test from IK4AUY with an Amplfier from RM. Zenki has given this manufacturer a couple of tilles. But lets go to the facts. IMD -46dB on 20m (as per ARLL add 6dB amateur IM3 method). This exceeds the specs of just about any radio, including the FT5000 in class A. Cleaner than anything around. The CB amplifier manufacturer does a better job. I am speechless, I don't know what to think of this.

500W out from the RM1000 BLA / IM3 -46dBc on 20m !!

See:
Quote
BLA1000 two tones RF  IMD test  with a newly low IMD  RF coupler design by I4SBX
at 500W pep out      (with 2x15W  CW RF tones coupled or 30Wpep RF in)
IM3 -46dBc

http://ik4auy.xoom.it/hf_tetrode_lin_amp.htm

Apparently not all CB gear is bad and not all HAM gear is good.
But this RM1000 BLA does an excellent job with 500W out.
Keep in mind that is 3dB better than the FT5000 in class A.(the best rig money could buy as far as IM3).

If you comment, PLEASE stick to the facts, no unsubstantiated claims and don't confuse it with rubbish about their other products. Stick to the topic.

73 Ron
VK4DD

PS If this was a CB amp, than it would have had a different name.
Like CB5000 DX, claming 5000 Watts.

##  IT IS smoke and mirrors !  And NO it's not even close to a yaesu 5000 in class A.  After  IMD-5, on my MK-V in class A... they are all down 80-90db.  This rm italy amp is not even in the same ballpark.   I would like to see this RM amp run at rated   1 kw pep out..then re-do the tests.

## I'd also like to see the yaesu VL-1000 being run at 1/2 rated power...and see what it's imd is.

I noticed nobody measured the eff of the RF amp, when being run at 1/2 power.  I bet it was lousy.  heck, lets run the icom amps, and all of the ss amps at 1/2 power..and measure the imd and eff on all of em.

##  The rm amp is 1/2 decent IMD..when run at 1/2 power.   My RL DRAKE  L4B, run at 1/2 power..at 625 w pep out is super clean IMD wise..and it's eff...and doesn't cost a trillion $$.  Plus it will handle high swr etc. ..and is cheap.  But it's  not a no tune.

##  "Zenki" can never display his callsign  for a specific reason.  Only I know who he really is.  Suffice to say he's the real deal..and no BS artist.  His true identity can never be revealed.

Later... Jim  VE7RF
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W1BR
Member

Posts: 4195




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« Reply #202 on: December 28, 2011, 08:49:52 AM »

The latest QST has a review of a TE 2M brick and they give it a -17dB 3rd and barely comment its not as good as they would like to see. The other ones aren't much better.
Jeez, how can they even accept advertising for that crap?? No conscience required when money crosses hands in ad revenue.

Carl

##  -17db pep.  Now that's  only -11 db  below one tone.   Now that is 4 x steps below crap. Seems to me most of these 2M brick amps are like this?   I have a small Mirage B310g...which has been around for eons,  but finally got into a qst review.  No mention of TX-IMD on ssb at all.  But they did mention that the FM/SSB  switch is to simply add .5 sec delay on ssb mode, when using the rf actuated  t/r relay.  I'm not 2m brick expert,  but it seems to me most of em are used for 2M FM.  That being the case, they probably bias em for class C...so the eff is good, and it minimizes temp on the heat sink.   Of course the imd will suck on SSB.  They could have easily installed a  DPDT switch, and used 1/2 of it to add the .5 sec delay, and the other 1/2 of the same switch to change the bias to linear class AB mode. 


## Later... Jim  VE7RF

Did Mirage ever post IMD specs for their amps? Most seem to be rated at power levels that are going well into gain suppression
for the devices they've used. Probably another case of where running them at 50% of advertised claims results in somewhat
useable IMD performance.

Pete
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VK4DD
Member

Posts: 79




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« Reply #203 on: December 31, 2011, 08:58:30 PM »

Hi,

No one publishes bad data. I quess we are addicted to good news
So if you don't see any IM3 numbers, you know that it is not a high end IM3 amp.
Expect something normal or even below that.

The question is what is normal IMD these days according to Ham standards.
Is that -30dB IM3 according to ARLL which is according to commercial standards -24dB.

What should we be aiming for?

Does a tube amplifier has got better IMD than a solid state amplifier?

For Zenki:

I had a browse through the fatboy site and I must say I had a great time.
I particularly liked the experimental spirit showing the big fan with 2 T antennas on the roof. Conclusion fat boy is a very creative person. Nothing wrong with that setup.

73 Ron.
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W1BR
Member

Posts: 4195




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« Reply #204 on: December 31, 2011, 09:58:25 PM »

[ I'm not 2m brick expert,  but it seems to me most of em are used for 2M FM.  That being the case, they probably bias em for class C...so the eff is good, and it minimizes temp on the heat sink.   Of course the imd will suck on SSB.  They could have easily installed a  DPDT switch, and used 1/2 of it to add the .5 sec delay, and the other 1/2 of the same switch to change the bias to linear class AB mode.  


## Later... Jim  VE7RF

Most of them use a reverse biased diode to set the bias. There is no thermal coupling between the diode and PA trasnsitor
packaging. Off course, that doesn't track the PA transistor worth a hoot, so the bias is all over the place.  Fred, N1DPM
wrote a paper on a bias system that replaces the passive diode used in the Mirage amps, with reportedly excellent results.
 
Pete
« Last Edit: December 31, 2011, 10:34:25 PM by K1ZJH » Logged
VE7RF
Member

Posts: 212




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« Reply #205 on: January 02, 2012, 03:47:18 AM »

Hi,

No one publishes bad data. I guess we are addicted to good news
So if you don't see any IM3 numbers, you know that it is not a high end IM3 amp.
Expect something normal or even below that.

The question is what is normal IMD these days according to Ham standards.
Is that -30dB IM3 according to ARLL which is according to commercial standards -24dB.

What should we be aiming for?

Does a tube amplifier has got better IMD than a solid state amplifier?

For Zenki:

I had a browse through the fatboy site and I must say I had a great time.
I particularly liked the experimental spirit showing the big fan with 2 T antennas on the roof. Conclusion fat boy is a very creative person. Nothing wrong with that setup.

73 Ron.


## -40db pep IMD3 is the min standard imo. Now, before some bozo rants on abt how many more $$ this is all gonna cost...relax, it won't cost hardly anything.  Then toss in the fact that hams have no problems at all, dropping 12,000 dollars on a xcvr with  -22 db pep TX imd....and  $200.00  G5RV dipoles....and huge $$ on useless baluns, etc, I'd say there is no excuse for lousy imd these days.

## If the FCC, etc can specify a min harmonic and spurious level, then they can also specify a bare min TX IMD level too.   I see absolutely no difference between those two. Grandfather all the old crap, plus any HB gear built b4 a certain date...and maybe 3-5 yrs down the road, we will see some improvements.

##  Just think about this. IF there were NO specified, mandated limits for say harmonic suppression, how much suppression do you think the various makers of ham gear would actually use ??  They sure as heck would not be using -60db LP Filters...maybe 25-30db...and that's the reality.

Later... Jim  VE7RF
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VK4DD
Member

Posts: 79




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« Reply #206 on: January 02, 2012, 01:54:46 PM »


## -40db pep IMD3 is the min standard imo. Now, before some bozo rants on abt how many more $$ this is all gonna cost...relax, it won't cost hardly anything.  Then toss in the fact that hams have no problems at all, dropping 12,000 dollars on a xcvr with  -22 db pep TX imd....and  $200.00  G5RV dipoles....and huge $$ on useless baluns, etc, I'd say there is no excuse for lousy imd these days.

## If the FCC, etc can specify a min harmonic and spurious level, then they can also specify a bare min TX IMD level too.   I see absolutely no difference between those two. Grandfather all the old crap, plus any HB gear built b4 a certain date...and maybe 3-5 yrs down the road, we will see some improvements.

##  Just think about this. IF there were NO specified, mandated limits for say harmonic suppression, how much suppression do you think the various makers of ham gear would actually use ??  They sure as heck would not be using -60db LP Filters...maybe 25-30db...and that's the reality.

Later... Jim  VE7RF

There was actually a time when amplifiers where <called> LINEAR amplifiers and for a good reason. Now we call them simply Power Amplifiers  probably because the linearity is lacking. A good tube like 8877 will have no problem achieving this, same can be said for the slightly more sensitive 3cx800. We can't use the 8877 because of our 400W limit.

Emtron will soon have the DX5 ready with almost 10KW, thats enough power for 20 Ham stations in VK. Who ever buys that must have good friends within the ACMA. You can say what you want but Rudy is a good tech, he knows how to make good power.

73 Ron.



« Last Edit: January 02, 2012, 01:58:13 PM by VK4DD » Logged
VE7RF
Member

Posts: 212




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« Reply #207 on: January 03, 2012, 03:19:45 AM »


There was actually a time when amplifiers where <called> LINEAR amplifiers and for a good reason. Now we call them simply Power Amplifiers  probably because the linearity is lacking. A good tube like 8877 will have no problem achieving this, same can be said for the slightly more sensitive 3cx800. We can't use the 8877 because of our 400W limit.

Emtron will soon have the DX5 ready with almost 10KW, that's enough power for 20 Ham stations in VK. Who ever buys that must have good friends within the ACMA. You can say what you want but Rudy is a good tech, he knows how to make good power.

73 Ron.




[/quote]

##  so exactly when is this DX-5  coming out ?    I see Emtron no longer lists a  DX-4 on their site ?  I thought that U folks in VK land will soon be getting ur power limit raised to 1 kw.  The ZL folks have 1 kw.  What u should be asking for is  power output parity with who ever has the most .  If rudy wants that dx-5 to work right, he seriously needs to dump this idea of using braid, between bandswitch and the tank coils.  If u are going to parallel bandswitch wafers,  then u have to do it correctly, so the current splits 50-50.  Taps go to wafer #1, closest to coils...and output of the entire mess is on the common of wafer #2.  A model 88 switch will work, providing you parallel at least 3 x wafers.  To make it into a shorting switch, all 3 x rotors have to be equipped with  multiple pole rotors. You need 5 pole rotor's..and not 4 or 6 pole either.

##  I see that HSU, from China will also be building a grid driven 4CX-10,000 as well.   Now these things would be the real ticket, 135 watts of drive for 14 kw pep out. IF they used the J version, the imd will be even better. 

Later...Jim  VE7RF
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VK4DD
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Posts: 79




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« Reply #208 on: January 03, 2012, 10:26:04 PM »

I dunno, I don't need one. I would assume that the braid he is using would be enough to run at least twice the US limit. How much thicker does it needs to be?

May be these leads where only for quick measurements driving the amp in reverse?
Just to show something to the public. He must have put it together in a hurry. I am sure that he knows what he is doing and how much a band switch handles. The model I have seen was for an exposition in Germany near the bodensee.

73 Ron.




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VE7RF
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Posts: 212




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« Reply #209 on: January 03, 2012, 10:55:12 PM »

I dunno, I don't need one. I would assume that the braid he is using would be enough to run at least twice the US limit. How much thicker does it needs to be?

May be these leads where only for quick measurements driving the amp in reverse?
Just to show something to the public. He must have put it together in a hurry. I am sure that he knows what he is doing and how much a band switch handles. The model I have seen was for an exposition in Germany near the bodensee.

73 Ron.

##  we already went through this with Dick, pa3duv, who has SEVERAL of the dx-3 and dx-4 amps. I mentioned to dick that the braid crap that rudy is using is a dead loss fro tank coil taps.  You can read abt it on the w8ji site.  It's also all over the emtron yahoo user site. Rudy would de-rate those amps to 1/2 power on 10m too.  The torroids used on the low bands were a dead loss too. Dick measured the temp of em at a whopping 229 deg C, using a Ir point and shoot..like my fluke 62.  Rudy has since re-designed the torroids, so they are not running at meltdown.

##  My buddy had run out of 1" wide, solid cu strap [ .032" thick]  for tank coil taps..and tried using some 1" wide braid instead. This is the stuff that's like 1/16" thick or less. This was on a 3CX-6000A7 GG amp..and on 15M.  What a disaster that was !  Flames and smoke everywhere.  It was yanked, and replaced with 1" wide cu strap.  I get the local metal shop to shear it for me in 3' lengths.  They have it locally in 3' x 7' sheets...and from .005" thick..right up to .125" thick.

##  dick, pa3duv found out that the tank coil and taps on his various emtrons were running blazing hot. And ditto with the model 86 switch.  On my slightly larger model 88 switch, you can buy optional "double commons"  so it grabs BOTH sides of the rotor hub, instead of just the top side.  Dick took his model 86 switch all apart in his big emtron dx-4's..and rebuilt it the way I suggested.  Presto, no more heat problems.  Getting rid of that stupid braid was the best thing you can do. It just adds  stray uh anyway.  All the various finding's were reported back to rudy, so he was well aware of it.

We also tried using wire  for taps on the adjustable tuned input of my GG 3CX-3000A7 amp..and that too was a disaster.  The wire adds way too much uh..even short pieces will do that.
Cu strap is unique, since it conducts RF on BOTH sides.  Hollow tubing only handles RF on the outside..and ditto with braided wire, solid wire. You can also fold wide cu strap into a "U"....so u get the benefit of  loads of surface area on both sides, and have it narrower, so it fits on a bandswitch, without getting close to adjacent contacts.  I have loads of pix of all this if you want to see em.

Later... Jim  VE7RF

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