Solved low power Tx Problem

General discussion and support for the Peaberry SDR V2.

Solved low power Tx Problem

Postby pilotcfii » Fri Mar 13, 2015 4:47 pm

After the last time I replaced the PA FET's in the PB (trying to get power out), David asked me to try his CW program and what-dya-know, I had 2W out CW. Then I set up to run digital, using HDSDR/vac/HRD/WSJT-X. I successfully got it all to work but only had about 200mW out. I made QSO's but very limited on power. David observed that since I had good power on CW Tx, that I may have a software problem. Good call. The only program layer that had any real control of the drive signal was vac.

Don't tell anybody but I read the directions for vac. Using those directions and some word I found elsewhere on the internet, I came up with the current settings. They are:
    Cables: 2
    Cable Parameters:
      SR: 11025...96000
      BPS: 8...32
      NC: 1..2
    Connected source lines: Line checked
      Ms per int: 7
    Stream fmt limit: Cable range
    Volume control: checked
    Enable channel mixing: checked
    Stream buffer watermark control:
    Enabled: Unchecked

All other settings are default.

I don't know if these are the best settings or not, but they worked and I was able to exceed 1W out, running JT65 & JT9. I have had a subsequent QSO, so I can't be too far off.

I hope this either helps someone else, someone else will help me make it even better, or both.

Thanks David for pointing me in the right direction.
73
Dan Malcolm
K4SHQ CFI/II
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Re: Solved low power Tx Problem

Postby pilotcfii » Fri Mar 13, 2015 5:41 pm

Since I solved the power problem, I am still left with a question. I can get a full watt out, but is that a good thing? JT65 is tantamount to continues CW key down for 48 seconds. On other rigs the max recommended power for JT65 is 30% to 50% to avoid damaging the transmitter. Unless someone can tell me different I am going to limit the power out to 500mW.
73
Dan Malcolm
K4SHQ CFI/II
pilotcfii
 
Posts: 130
Joined: Sat Dec 07, 2013 6:52 pm
Location: Alabama

Re: Solved low power Tx Problem

Postby TerryFrench » Fri Mar 13, 2015 8:31 pm

I think the Peaberry was designed to handle digital modes. So (and it's only my own personal opinion) it could likely handle 100% key down forever.

The whole duty cycles is for everything else you might use that was built with undersized (IMO) specs so that one can have a 100W transceiver (or a x W amp / Tuner...) knowing the modes that HAM operators would use. Digital modes really changed these assumptions. These other pieces of HAM hardware would cost more and need beefier design/parts to handle continuous operation at their maximum power rating. The manuals are usually clear on what power level can be used.

So the Peaberry should be fine (I have not had any problem so far, and never heard of any problem driving the Peaberry to its full legal power (i.e. without populating the extra PA FET). If you then drive an amp, make sure the amp is ok with 100% duty cycle.
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Re: Solved low power Tx Problem

Postby pilotcfii » Fri Mar 13, 2015 9:10 pm

Thanks Terry,
It's as I thought but I didn't want to risk the PA. It's not that hard to replace the FET's but it's not desirable either.
73
Dan Malcolm
K4SHQ CFI/II
pilotcfii
 
Posts: 130
Joined: Sat Dec 07, 2013 6:52 pm
Location: Alabama

Re: Solved low power Tx Problem

Postby W4MMP » Sat Mar 14, 2015 12:08 am

Hi,
Yes I agree with Terry. A Peaberry can be run full tilt for a very long time. I performed a few temperature test/measurement and the PA final temperature maxed out at about 75°C well under the max of 150°C
73
Ron / W4MMP
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Re: Solved low power Tx Problem

Postby pilotcfii » Sat Mar 14, 2015 2:56 am

What power out are you calling "full tilt" I am running at 1W but could potentially get 1.5W out. The single watt seems to work quite well as I hit propagation just right and logged Austria using the PB and JT65.
73
Dan Malcolm
K4SHQ CFI/II
pilotcfii
 
Posts: 130
Joined: Sat Dec 07, 2013 6:52 pm
Location: Alabama

Re: Solved low power Tx Problem

Postby W4MMP » Sat Mar 14, 2015 9:12 am

One (1) watt. I would not recommend running higher than 1 watt as there is the potential to drive the PA into non linearity.
73
Ron / W4MMP
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Joined: Fri Jan 03, 2014 3:31 pm
Location: Lovettsville, Virginia FM19EG

Re: Solved low power Tx Problem

Postby pilotcfii » Sat Mar 14, 2015 5:14 pm

Ok good. That's where I have it set now.
73
Dan Malcolm
K4SHQ CFI/II
pilotcfii
 
Posts: 130
Joined: Sat Dec 07, 2013 6:52 pm
Location: Alabama

Re: Solved low power Tx Problem

Postby KC8UD » Mon Mar 16, 2015 12:26 am

I'm not certain of my power out, probably around 1 watt, but I've had no problem running JT65 or PSK31 or even RTTY, Olivia and other digital modes which sometimes require key down times of at least a minute or so. This rig can routinely make contacts all around the world. The heat sink has never gotten warm. It's always cool to the touch. The only parts that are ever warm are the voltage regulators and they are always HOT! I don't think you'll have any problem at one watt on your unit with long key down times.

Gary
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