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Author Topic: PSK with 30L-1?  (Read 7495 times)
W5DQ
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« Reply #15 on: June 15, 2012, 01:46:00 PM »

Hello,

   After being off the air for about 12 years, I'm back.   Pulled my 30L-1 out of storage, cleaned it off, vacuumed it out,
washed the tubes in running water, cleaned the switch contacts, oiled the fan, brought it up with a Variac over about a day.  All OK.

Did you have it stored in a mineshaft? Why so dirty to need a bath???

Quote

PSK is a new, fascinating mode on the bands.  It works with my computer sound card.  It's like a whole ham band in the space of a single SSB signal.  With a relatively modest antenna ( 5BTV vertical ) pounded into the hillside behind my house, many people cannot hear me. 


Yeah for the last 10-12 years  Roll Eyes

Quote

   So I tried QRO... according to data on the Net, PSK is not especially efficient WRT really low signals - it's just a bit better than RTTY.  Just like SSB - people can't hear me, push the big switch on the 'L-1, and suddenly they CAN hear me. 

   But the 30L-1 is definitely not happy with that mode.  Even running reduced power, it gets really hot.   I gave up
on that.  Maybe it's time for a new linear.   There's a local guy with a fair deal on an Ameritron AL-80B.  Pop goes the egg money! 

   Or maybe the 30L-1 could be modified?  I can get a matched set of four Chinese 572B's for $200 from IIRC RF Parts.  And then maybe paint the inside of the final cabinet flat black for better infrared heat transfer?  And keep the power down to maybe 300W?  Anybody out there doing RTTY or similar with a 30L-1?

                                                 - Jerry Kaidor, KF6VB


So I tried QRO ..... Bet you made alot of friends that day!!  Shocked

PSK31 is typically run at less than 50 watts, usually around 25 or less. Like was mentioned, if you can't be heard at 50W or less, then you're antenna system is probably a real DOG!! And yes, regardless of what you read or hear others say, unless your QTH has 'golden soil type' for vertical operations, you're going to need radials. The more the better up to around 30-40 minimum. I believe the typical recommendation is upt to 60 or so for the typical soil conditions in the US unless you're in a salt marsh or on the beach. A stake driven in the ground is TOTALLY USELESS in most instances except to mount the antenna to. Even a long ground rod won't do the trick unless you are extremely lucky. I run a 6BTV with 48 radials and even though I get good results, I still think it is marginal and could use a few more radials to improve it.

"according to data on the Net, PSK is not especially efficient WRT really low signals " Huh ....... not sure where you're reading but the typical PSK31 station runs a wire antenna and low power and has little to NO problems in successful ops with other stations.

Last point ..... DO NOT RUN AN AMP ON PSK31  Angry

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Gene W5DQ
Ridgecrest, CA - DM15dp
www.radioroom.org
K8AC
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« Reply #16 on: June 15, 2012, 03:04:49 PM »

Quote
*** I don't see why.  500W is about 12db more than 30W.  Make that 4 S units.
Would it be more socially acceptable if I ran 30W into stacked Yagis?  Point them at you, it's the same 12 db.

   As far as "wiping out the band" is concerned, the important thing IMHO is to keep it clean.  Don't overdrive anything.  Try not to see any ALC reading.  Nowadays, everybody has waterfall displays, and they can see when you splatter all over the band.

                                           - Jerry Kaidor, KF6VB

Jerry - if you want to fit into the PSK world, you're going to have to understand a few things and accept others that you won't necessarily like.  Here are some points:

1. The two tones used for PSK will result in IMD products that cause interference that would be less of a problem in other modes.  In a "good" station, your third order IMD products will be down only 30 dB or so from the two tones.  That means that you'll have a sideband spaced on each side of the two tones, but it won't be that much of a problem as long as your signal is not strong.  The fact is that many stations have a third order IMD of closer to -20 dB and that results in higher order IMD products (more sidebands).  It doesn't take much to end up with a signal that's 10 times as wide as the 31 Hz spacing you started out with.  In SSB mode, such products would be filtered out by the transmit filter, but in this case the PSK signal (with all it's distortion sidebands) fits quite nicely within the filter bandwidth and they all come through unaltered.

2. With weaker signals, the chances of a dirty signal's sidebands interfering with other PSK signals is much less.  With you running 1,000W on PSK, your IMD sidebands (even at -30 dB) will obliterate weaker signals anywhere close to your frequency.

3. At the risk of alienating other PSK users, I will tell you that the average PSK operator has little or no understanding of how receivers, AGC, narrow filters, etc. work and cannot properly apply them to a situation.  They typically are receiving with an SSB filter of 2.4KHz or greater bandwidth and so an extremely strong signal in that passband will de-sense their receiver and effectively obliterate other signals.  An experienced operator at that point would crank in a narrow filter and thus escape the problem.  But, many of these users are running transceivers that don't have CW filters and few know how to use passband tuning or IF shift to accomplish narrower selectivity.  

4. Even if the operator understood the options and had the capability of narrowing down his passband, even that would not allow him to escape from your strong sidebands, which would still clobber weak signals.  

We can talk about this all day, but I think the most effective thing is to see images of some PSK signals that are too wide, either because of poor IMD or extreme strength (don't forget, the IMD products are, at best, only 30 dB or so down).  Take a look at this page:

http://www.k8ac.net/signal_images.html  and scroll down a screen or so to see the results of strong or overdriven PSK signals.   While most of the bad signals seen there had poor IMD, the effect would be similar for someone running PSK with what's considered "good" IMD.  Transmitters should have better IMD performance, but they don't.

73, Floyd - K8AC
« Last Edit: June 15, 2012, 03:08:02 PM by K8AC » Logged
KB4QAA
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« Reply #17 on: June 15, 2012, 04:18:45 PM »

PLEASE do NOT run more than 30 watts on PSK - that will just about wipe out the band!!!

*** I don't see why.  500W is about 12db more than 30W.  Make that 4 S units.
Would it be more socially acceptable if I ran 30W into stacked Yagis?  Point them at you, it's the same 12 db.

   As far as "wiping out the band" is concerned, the important thing IMHO is to keep it clean.  Don't overdrive anything.  Try not to see any ALC reading.  Nowadays, everybody has waterfall displays, and they can see when you splatter all over the band.

                                           - Jerry Kaidor, KF6VB
The reason your amp is burning up is all the hate and anger of the band karma being returned to you for your discourteous ways.  Wink

The problem is you really DON"T understand PSK and it's nature.  PSK is not a perfect mode.  It doesn't tolerate strong adjacent signals, regardless of how clean they are.

If you can't make contacts with 30 watts.....accept it.  Using an amplifier is frankly Liddish and selfish behavior.   Fix up your antenna system for best performance, rather than waste time on the amp.   CUL

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W5DQ
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« Reply #18 on: June 15, 2012, 04:45:05 PM »

A 5BTV pounded into the ground is not going to perform well on any mode. You need ground radials, not just a single ground rod.

Not true I have used one for many years and is does a decent job.


Decent is a relative term. I can make contacts using a 100W light bulb on a fence post but I don't think I would consider that an optimal antenna system.

You should consider yourself REALLY lucky to have EXCELLENT soil/ground type to achieve anything that would be considered DECENT as far as antenna effectiveness with a vertical and a single ground rod as that goes against EVERYTHING written about using a vertical antenna.

Not to say your vertical antenna system is one but one can make contacts on a crappy vertical setup but most likely more contacts on a properly installed and configured one.

Gene W5DQ
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Gene W5DQ
Ridgecrest, CA - DM15dp
www.radioroom.org
W8JX
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« Reply #19 on: June 15, 2012, 06:44:52 PM »

A 5BTV pounded into the ground is not going to perform well on any mode. You need ground radials, not just a single ground rod.

Not true I have used one for many years and is does a decent job.


Decent is a relative term. I can make contacts using a 100W light bulb on a fence post but I don't think I would consider that an optimal antenna system.

You should consider yourself REALLY lucky to have EXCELLENT soil/ground type to achieve anything that would be considered DECENT as far as antenna effectiveness with a vertical and a single ground rod as that goes against EVERYTHING written about using a vertical antenna.

Not to say your vertical antenna system is one but one can make contacts on a crappy vertical setup but most likely more contacts on a properly installed and configured one.

Gene W5DQ

Well 20+ over 9 on 40 is not "crappy" by any means. I think it is a combination of soil type, antenna location (on a hill) and ground (rod) actually being a 7 foot fence pole with a wide spade at bottom driven 6 feet into ground. It holds its own and then some on 40.
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K1ZJH
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« Reply #20 on: June 16, 2012, 07:36:23 AM »

Is turn around time a consideration for PSK?  I'd expect that old amp probably uses very slow relays for
antenna changeover.

Just curious..
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W8JX
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« Reply #21 on: June 16, 2012, 09:56:53 AM »

Is turn around time a consideration for PSK?  I'd expect that old amp probably uses very slow relays for
antenna changeover.

Just curious..


Not at all. It is "key down" mode. Pactor, Amtor ARQ and Clover are a few of the modes where turn around is a issue.
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KF6VB
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« Reply #22 on: June 17, 2012, 06:51:33 AM »

Hello,

   After being off the air for about 12 years, I'm back.   Pulled my 30L-1 out of storage, cleaned it off, vacuumed it out,
washed the tubes in running water, cleaned the switch contacts, oiled the fan, brought it up with a Variac over about a day.  All OK.

Did you have it stored in a mineshaft? Why so dirty to need a bath???

*** There was dust "stuck" to the tubes that would not come off with just
blowing and vacuuming.  So I rinsed it off.  Just the tubes, not the amp.  Everything else I cleaned with vacuum and blowing and a little brush.

                                        - Jerry


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KF6VB
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« Reply #23 on: June 17, 2012, 06:54:44 AM »

A 5BTV pounded into the ground is not going to perform well on any mode. You need ground radials, not just a single ground rod.

Not true I have used one for many years and is does a decent job.

PSK31 is meant to be a low power mode, 30 watts or less. No need for anymore power than that.

Most times this is quite true but there are times when even 100 watts is not enough. The reason most run low power is also because rigs get quite warm during transmission as it is basically constant key down. 


Fix your antenna and run 30 watts. I have never run anymore than 25 watts on any digital mode other than RTTY and Hell.

Again conditions is a factor too at times.

When there is not propagation you are not going to make contacts with 1000 watts. We all know that. However I have never had to run more than 30 watts on PSK31. If conditions are not right you will not make contacts.

IMO using an amp for PSK31 is inconsiderate of others using the frequency.
*** OK, the antenna was crappy.  I fail to see how running high power with a crappy antenna is less "considerate" than running low power with a good antenna.  It's the same RF at the other end.

   Since then, I have been gradually adding radials to the system.  I also
moved it up to the top of my hill.  So I probably won't need the high power
any more.

                                - Jerry


                                        - Jerry


Sure a trap vertical will work without radials. But a dummy load works too. We all know that radials are the 2nd half of a vertical antenna. You state your vertical does a decent job? So does a G5RV at 15, friend of mine has to use his at that height. But we all know it would work better at 55 feet.
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W8JX
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« Reply #24 on: June 17, 2012, 08:45:24 AM »

Sure a trap vertical will work without radials. But a dummy load works too. We all know that radials are the 2nd half of a vertical antenna. You state your vertical does a decent job? So does a G5RV at 15, friend of mine has to use his at that height. But we all know it would work better at 55 feet.

After being a "Ham" for 43 years I have had good and bad antennas. I know from experience that this one does work quite well as dummy loads do not return 20 to 30 over 9 reports on 40m at times. Would radial help? they likely would some but in my case I do not see them adding a S unit or more as current "math" does not support it on 40m.
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K7MH
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« Reply #25 on: June 17, 2012, 11:21:52 AM »

A 5BTV pounded into the ground is not going to perform well on any mode. You need ground radials, not just a single ground rod.

Not true I have used one for many years and is does a decent job.


Decent is a relative term. I can make contacts using a 100W light bulb on a fence post but I don't think I would consider that an optimal antenna system.

You should consider yourself REALLY lucky to have EXCELLENT soil/ground type to achieve anything that would be considered DECENT as far as antenna effectiveness with a vertical and a single ground rod as that goes against EVERYTHING written about using a vertical antenna.

Not to say your vertical antenna system is one but one can make contacts on a crappy vertical setup but most likely more contacts on a properly installed and configured one.

Gene W5DQ

Well 20+ over 9 on 40 is not "crappy" by any means. I think it is a combination of soil type, antenna location (on a hill) and ground (rod) actually being a 7 foot fence pole with a wide spade at bottom driven 6 feet into ground. It holds its own and then some on 40.

I had a 4BTV in the ground with no radials at one time.
When I moved it to the roof and added radials it was FAR better, no comparison at all.
20+ over S9 on 40 where? In the next state or the Persian Gulf??
If it works for you, that's great but It is about as minimal an antenna as it gets. Have you ever used anything to compare it with?
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W8JX
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« Reply #26 on: June 17, 2012, 11:42:13 AM »

I had a 4BTV in the ground with no radials at one time.
When I moved it to the roof and added radials it was FAR better, no comparison at all.

Many do not have the ideal location for a vertical like I do. In most directions it has pretty much line of sight to horizon. from SE to NW the antenna is 50 to 100 feet above valley floor within 50 to 150 yards.

20+ over S9 on 40 where? In the next state or the Persian Gulf??
If it works for you, that's great but It is about as minimal an antenna as it gets. Have you ever used anything to compare it with?

I had wire antennas up in past and this vertical was "supposed" to be temporary but it played so well on 40 and 80 I left it up. I have worked all through Europe and 40 and 80 with consistent S9+ signals. I have been down under many times with it and usually 59+ as well. State side it plays really well on 40 and many times I will start a QSO and others join in to comment on strong signal during day. It is not as strong on 20 and above and there is room for improvement there but I spend little time on those bands these days. 
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W5DQ
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« Reply #27 on: June 18, 2012, 09:58:46 AM »

A 5BTV pounded into the ground is not going to perform well on any mode. You need ground radials, not just a single ground rod.

Not true I have used one for many years and is does a decent job.


Decent is a relative term. I can make contacts using a 100W light bulb on a fence post but I don't think I would consider that an optimal antenna system.

You should consider yourself REALLY lucky to have EXCELLENT soil/ground type to achieve anything that would be considered DECENT as far as antenna effectiveness with a vertical and a single ground rod as that goes against EVERYTHING written about using a vertical antenna.

Not to say your vertical antenna system is one but one can make contacts on a crappy vertical setup but most likely more contacts on a properly installed and configured one.

Gene W5DQ

Well 20+ over 9 on 40 is not "crappy" by any means. I think it is a combination of soil type, antenna location (on a hill) and ground (rod) actually being a 7 foot fence pole with a wide spade at bottom driven 6 feet into ground. It holds its own and then some on 40.

So is EVERY signal on 40M is 20+ over 9 or is that the average signal strength or the mimimal signal strength. I had a 1/4 wave 40M vertical that had flat SWR with only a couple of radials and it provided some loud signals. Before I did more testing and some detail analysis, I thought that was a good antenna as I had some strong RX signals. But then the same signals were strong on all of my antennas, cut for 40M or random length.  But after some time operating it and poor results, I did some test/measurements and found the transmit radiation pattern was a real crapper. After I changed out the antenna with a 6BTV (modified with a large top hat to broaden up the SWR curve and increase efficiency) and added about 45 more radials to the field, I now have what I would call a decent (but still far from optimal) vertical setup. But at least I can hear and be heard with it.

According to almost every text I have read concerning vertical antennas, your 6 foot ground rod does very little RF wise to help your vertical radiation efficiency. Your setup being a hill probably adds more to the results especially if the down hill slope is at a steeper angle than a 6' ground rod. But stating a 20+ over 9 RX signal really doesn't speak anything about your antennas radiation efficiency which is what radials help optimize by lowering the radiation losses.

But congrats on your remarkable setup. Like I said previously, you should consider yourself extremely lucky to have such an 'non-crappy' setup with only a ground rod as the other half of the antenna.  Most vertical installation can't say they have such a great setup with only a ground rod and no radial field.

Gene W5DQ
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Gene W5DQ
Ridgecrest, CA - DM15dp
www.radioroom.org
M0HCN
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« Reply #28 on: June 18, 2012, 11:22:35 AM »

The thing is that on HF receive performance is usually sky noise limited, in that with a good aerial most receivers are far more sensitive then is really needed given the QRN levels on the lower frequency bands.
Because of this a poor aerial really does not hurt you on receive all that much because the QRN comes down by the same amount your wanted signals do, and both are usually well above the receivers noise floor.
Note that the implicit assumption above applies only on HF, VHF and above has lower QRN so the rx noise performance plays a bigger role.

The same thing however cannot be said on transmit, where the poor aerial directly impacts the SNR at the other guys receiver, here having an aerial that is 10dB or so down on what it could be really can push you into needing an amp to get heard on the nominally low power modes.

While it could possibly be argued that using an amp to compensate for a poor aerial system is in some sense inelegant, it is not in fact an unreasonable strategy even for PSK or the like. Obviously the amp must be clean, but that really should be the objective anyway.
30W into a good aerial is indistinguishable in the far field from 300W into a poor one, but  particularly on the lower frequency bands both will let you hear pretty much the same stations.
 
Regards, Dan.
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K8AC
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« Reply #29 on: June 18, 2012, 11:44:33 AM »

Quote
While it could possibly be argued that using an amp to compensate for a poor aerial system is in some sense inelegant, it is not in fact an unreasonable strategy even for PSK or the like. Obviously the amp must be clean, but that really should be the objective anyway.

For PSK mode, I must disagree with this.  Using an amp IS an  unreasonable strategy for PSK for a variety of reasons.  The most important being that IMD in PSK mode isn't some imaginary thing that may happen or not.  Even when unmodulated, an idling PSK signal with less than excellent IMD has sidebands that will interfere with adjacent stations.  Often, we hear someone use the term "clean" as you have here applied it to amplifiers.  It might surprise many to learn that some common and expensive amplifiers have IMD ratings that aren't exactly excellent.  For example, the Acom 2000 (IMD rated at 31 dB), Icom PW1 (IMD rated at 29 dB).  Would you say those are "clean" amplifiers in terms of IMD?  Using an amplifier for PSK mode is just a bad idea, even with a poor antenna. 

73, Floyd - K8AC
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