Output Power

General discussion and support for the Peaberry SDR V2.

Output Power

Postby RichardP » Sat Aug 23, 2014 3:14 pm

Hi there,

Peaberry v2 using an FM transmission and measured on the output...

14Mhz - 1.5Watt
10Mhz - 2.2Watt
7Mhz - 2.2mWatt
5Mhz - 2.2Watt


1.5W looks paltry compared on the output on the most popular band... what can I do/look for to get it up to the same as the other bands? (Is it another build mistake?)

Best Regards,
Richard
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Re: Output Power

Postby kz1x » Sat Aug 23, 2014 4:24 pm

Sounds like you have a good working setup.
Those levels seem right on.
Did you install the 2nd set of output FETs?
What is the drain voltage when you are in full TX? (Measure on the cold side of the choke).
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Re: Output Power

Postby W4MMP » Sat Aug 23, 2014 5:41 pm

Hi,

Make sure your supply voltage is set to 13.8V. I was running my Peaberrys at 13V. The .8V made a significant difference in the output power.
73
Ron / W4MMP
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Re: Output Power

Postby RichardP » Mon Aug 25, 2014 8:43 am

kz1x wrote:Sounds like you have a good working setup.
Those levels seem right on.
Did you install the 2nd set of output FETs?
What is the drain voltage when you are in full TX? (Measure on the cold side of the choke).

I only installed the FETS as per manual (three of them) - The other two footprints are still open. (The packet came with 4X fets for some reason).

the Instructions show to install Q6/Q7/Q8 - .. I just cant find where on the schematic Q6 is..

On the Choke in question, can you please elaborate which choke and the hot side please?



W4MMP wrote:Hi,

Make sure your supply voltage is set to 13.8V. I was running my Peaberrys at 13V. The .8V made a significant difference in the output power.

that is a certain :D Bench PSU pegged on the volage.

Thanks all!
Regards,
Richard
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Re: Output Power

Postby kz1x » Mon Aug 25, 2014 12:26 pm

Measure at the junction of T5 and L10.

When going through a kit like this in a diagnostic analysis, it is often a good idea to consider the functions of each component as you examine the overall operation of the radio.

For example, the schematic shows +12 on one end of L10. Start there.

Of course, the designer meant to have that say "13.8" or better "14" but don't get lost in semantics.

L10 stops any vestige of RF that crept out of T5 from appearing on the power line. It does so at the risk of adding I^2R losses; all of life is a series of choices/compromises and electronics is no different. The capacitors at that junction also serve to control that node: the electrolytic adds some bulk capacity for lower frequency transients and the small cap is a path to ground for high frequency energy.
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Re: Output Power

Postby kz1x » Mon Aug 25, 2014 12:36 pm

RichardP wrote:
(The packet came with 4X fets for some reason).

the Instructions show to install Q6/Q7/Q8 - .. I just cant find where on the schematic Q6 is..



Q6 is on page 2 of the schematic, at location "C - 4" . It is part of the PA bias circuit.
The schematic uses 'circle' symbols for bipolar transistors but not for FETs.

And, I assume the extra FET is to experiment with, a spare for failures, or some other reason David did not share.
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Re: Output Power

Postby RichardP » Wed Aug 27, 2014 7:29 pm

I give up,
the hours spending fault finding and not being with my kids is not worth the effort of this creation.
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Re: Output Power

Postby kz1x » Thu Aug 28, 2014 1:24 am

I have been reading your posts, and understand the frustration.

I also saw the other posting about recommending that this radio be purchased pre-built! I can also see how one would arrive at this conclusion.

To be frank, and this is not meant expressly for you or to anyone in general nor it is an indictment: I think that this the Peaberry series of kits has proven to me that the larger market for kit radios is not well suited to surface mount assembly. This is despite the best efforts in kitting by David, and to the extent that he could, to design in several steps of B-I-T-E (built in test equipment).

I and a number of others with extensive experience and well equipped assembly and diagnostic abilities are not representative of the larger market, and for me to say that all three of my Peaberry radios went together in a few hours and worked the first time sounds like braggadocio to others. Understandably, most unnerving to the ears of those who have struggled! For those people, or for whom the time isn't worth the assembly experience, the assembled radio is a bargain.

On the other hand, the radio can in fact be assembled by hams, and work right off. That's certainly the well-demonstrated case. So, I can neither wholesale-endorse the need to get it pre-built, across the board.

I am just now learning what your working conditions are, and they would be called, in golf vernacular, a handicap.

In the other thread you started, I will make some suggestions to vastly reduce your frustration level and get you closer to a working radio.
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Re: Output Power

Postby KC5SB » Thu Aug 28, 2014 1:55 am

Richard:

Put the kit aside for a few days and play with the kids. Forget about the Peaberry for a while and when you feel like it return with a refreshed attitude. I have built lots of equipment over 54 years of hamming and the Peaberry was among the most challenging. However, I kept at it and with the help of others on this forum and a lot of patience I got the little rig to work as advertised - it was worth the effort. Almost ALL problems with this build are related to soldering. A strong magnifier of some sort is a requirement. Access to an oscilloscope was very helpful to me also, but many have built the kit without one.

Good luck,

Bill, KC5SB
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Re: Output Power

Postby RichardP » Thu Aug 28, 2014 7:38 am

I really dont want to give up ... so here is the status... Apologies for the outburst but i thought I was on the right track and was just needing the SWR meter to tune my radio - Only to discover that its not even working there.

The output is unknown - On a spectrum analyser I see a spike at the centre frequency that does not change even when not transmitting.. and when TX is selected stuff happens on eiher side of the centre... - When I transmit the FETS get warm (expected) but I dont get anything worth while using on the output.

UPDATE:
L10 - Drops less than 200mV across it when transmitting

https://picasaweb.google.com/1051621755 ... directlink

A trace of AM and FM transmission of a single tone .. measured over the 50ohm load on the output... the Amplitude is almost never constant in FM mode (I expect it to be)

Richard
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