Output transmit garbled

General discussion and support for the Peaberry SDR V2.

Re: Output transmit garbled

Postby kd5kll » Tue Apr 07, 2015 1:41 am

Just an update: I was worried for nothing.

I have made several JT65, JT9, and PSK31 contacts on both 20M and 15M. All of them have been to stations in the lower 48, but I'm still impressed.

AE9RB, you designed a nifty little radio that was a lot of fun to build. When the oscilloscope gets here, I'll do a little more tweaking and tuning, but I think I'm going to have fun with this radio. This is the first HF I have worked since my college days, when I could use the W5GB club radio when I didn't feel like studying...

It's nice to be able to work HF from home. It will really be nice to work HF from hotel rooms via VPN connection back to the house!
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Re: Output transmit garbled

Postby kd5kll » Tue Apr 07, 2015 9:50 pm

I now have a handy Digital Storage Oscilloscope to test my radio.

I hooked my probe across the 50ohm dummy antenna and measured FM transmit on all four bands. Nice clean sine wave on all four, but the voltage values didn't make much sense:

30M 10.140 - 150Vp-p 48Vrms
20M 14.070 - 90Vp-p 30Vrms
17M 18.100 - 44Vp-p 14Vrms
15M 21.076 - 38Vp-p 12Vrms

Using (Vrms)^2 / 50 = Power:

30M 46W
20M 18W
17M 3.92W
15M 2.88W

Obviously, I'm not measuring something correctly.

Any ideas?
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Re: Output transmit garbled

Postby W4MMP » Tue Apr 07, 2015 9:54 pm

Hi,
A scaling issue I believe. Is your probe set for X10 and your scope set for X1?
73
Ron / W4MMP
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Re: Output transmit garbled

Postby kd5kll » Tue Apr 07, 2015 10:22 pm

Yep, that was it.

I also noticed that the probe only has a bandwidth of 6MHz at 1X.

I set the probe and the scope for 10X and I get the following values:

30M 30V p-p 10V rms 2W
20M 28V p-p 8V rms 1.28W
17M 15.4V p-p 5.2V rms 0.5W
15M 15.2V p-p 5.2V rms 0.5W

So, is that about normal for a 30/20/17/15 build?
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Re: Output transmit garbled

Postby W4MMP » Tue Apr 07, 2015 10:42 pm

Yes, I have the same build and your power values are pretty much in line with mine. Have fun with your new Peaberry. It is a great rig.
73
Ron / W4MMP
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Re: Output transmit garbled

Postby kd5kll » Wed Apr 08, 2015 2:53 am

I made a few 15, 20, and 30M QSOs tonight on JT65.

I think my next step will be building a couple of Hardrock 50 drivers (one for 15/17, an the other for 20/30) to get my output up to 10W.
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Re: Output transmit garbled

Postby W4MMP » Wed Apr 08, 2015 3:01 am

Congrats on your contacts.

Hum, Why would you need more that one?
At any rate, you will need low pass filtering for the Hardrock driver board.
73
Ron / W4MMP
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Re: Output transmit garbled

Postby kd5kll » Thu Apr 09, 2015 4:38 pm

W4MMP wrote:Hum, Why would you need more that one?
At any rate, you will need low pass filtering for the Hardrock driver board.


The Hardrock 5W/10W driver board has a place to put a low pass filter directly on the board, but it only works for two bands. I realize that I could forgo the direct low pass filter on the board and have a separate selectable low pass filter board. But for the cost, it seems to me to be just as cheap to buy two driver boards at $35 each and the miscellany needed for the two low pass filters, and just build one for 15/17 and one for 20/30.

But I'm still investigating. Anything I do at this point has to come out of next month's hobby allowance. April's money is spent.
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Re: Output transmit garbled

Postby W4MMP » Thu Apr 09, 2015 4:52 pm

Ah, OK I see. Thanks for the info.

Great guys over at hobbypcb.com . When I contacted them about using the driver with the Peaberry and my particular set up, Jim redesigned the filter for a cut off about 15 Meters. The driver works great.
73
Ron / W4MMP
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Re: Output transmit garbled

Postby kd5kll » Thu Apr 09, 2015 6:47 pm

I would worry that the LPF for 15M wouldn't keep the 30M second harmonic suppressed enough, or at all. I've been having fun on 30M. Have you measured to see what you are putting out on the second harmonic when working 30M?
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