[NLRS] Thoughts on VHF-UHF beacon hardware - key clicks.

[Lloyd Berg - N9LB]

When making a beacon, make sure you incorporate some shaping into the CW
keying waveform otherwise you will have a wideband garbage generator
throwing "key clicks" all over the band.

-----Original Message-----
From: NLRS [mailto:nlrs-bounces at mailman.qth.net]On Behalf Of David Palm
Sent: Friday, July 17, 2015 7:51 AM
To: NLRS List
Subject: Re: [NLRS] Thoughts on VHF-UHF beacon hardware.

Doug,

You're touching on a topic that keeps surfacing for me as well: beacons.
I'm just turning my attention back to VHF-UHF-SHF as some matters clear up
here at home and in fact tried an on-air test with K2DRH the other day with
my homebuilt W1GHZ transverter. Not yet successful in making contact
(that's a 140 mile path for 900 MHz), but the goal is at least to get the
footprint on 902 and 1296 and rework the antennas here on the lower bands.
I'm going to work on the 902 'verter again today over the lunch break.

All that to say that I keep coming back to the idea of beacons as well.  My
QTH is ideal for them.  My farm sits atop one of the tallest ridges around
here and I have a silo on the property with the dome at about 70 feet above
ground level.  So it would be relatively straightforward to pull power up
there, set equipment on a platform just under the dome, and have an amazing
beacon array.  The one time I had a beacon going I got signal reports from
a very large radius -- the problem was that it was banging away from an
antenna on my roof and disrupted even local repeater usage for us.

My thoughts are running somewhat along the lines you've outlined and
diverge in ways.  I would like to use an Si570 to generate the initial RF
on 144, 222, and 432 (902 and 1296 would be possible too, with the parts
that I have.)  I thought of using a Raspberry Pi to change frequencies and
generate the CW keying.  This would also give me the ability to connect to
that beacon controller via WiFi for software update, resetting or powering
down the equipment, etc.  Then I would use a small MMIC to get the Si570
output up to the 10 dBm range and use that to drive power amplifier modules.

The digital modes you describe would really ice the cake, but I currently
lack the understanding of how those might be generated in the context of
the beacon system I've just described.

I have most of the hardware to accomplish this -- Si570 in the QRP2000
configuration, Raspberry Pi, 4 - 1 coaxial relay, MMIC amp stages, and have
started gathering the small amplifier modules to get a 20ish watt footprint
on each of those bands.  What I lack is the time to pull it off.  But, I've
done all kinds of sketches and it's fun to dream about at least.  Perhaps
someday you'll hear W9HQ/B back on the air again.  Let's stay in touch on
the matter.

73,

David  W9HQ


On Thu, Jul 16, 2015 at 12:14 PM, Doug Reed <n0nas at amsat.org> wrote:

>
>
> I've been debating with myself what might be the cheapest way to get a
> VHF-UHF beacon on the air without having to dedicate an expensive SSB
> rig to the task and without buying crystals. I keep coming back to
> using modes like CW or PI4/JT65/WSPR that work with a Class C RF
> amplifier, then use an old FM mobile as the TX and power amp. You can
> use crystal control, but crystals are getting difficult and expensive
> to buy. But it is fairly easy to do if the beacon controller also
> provides the frequency control and stability. The HansSummer.com
> Ultimate 3S controller can handle all of that, especially with the
> optional OCXO SI5351A oscillator and using GPS for frequency control
> and timing.
>
> I've been a bit more worried about how to do propagation RX monitoring
> from the same site, if I wanted to.... The FM receiver is useless for
> that, but with the SI5351A oscillator acting as a LO for the receiver
> front-end and mixer, I could feed the IF out to a "cheap" HF receiver
> such as a SoftRock, Minima, Pixie, or even a CB SSB radio. Anything
> that receives CW or SSB would work to feed audio to the sound card RX
> software for decoding. Another option would be to just use the FM
> receiver front-end as a filter with a RTL-SDR dongle as the
> receiver....
>
> If anyone wants to try this or other direct keying mods to build a
> beacon site, VHF and UHF crystal-controlled mobiles are available
> pretty much for the hauling. Nobody wants to buy crystals. 6M is a
> little harder to find because you have to be sure you get a "high
> split" radio.... In fact the problem may turn out to be that many or
> most of these mobiles are 110W radios and they seem like a bit of
> overkill for a beacon....
>
> One thing to remember, the FM mobiles were designed for intermittent
> duty, around 20% TX. Unless you reduce power, add fans and heat
> sinking, or built an intermittent TX beacon, you will have problems
> with overheating the TX. OTOH, I have successfully modified a 110W GE
> mobile to run FM repeater continuous duty with just extra heat
> sinking. I then added fans to be 100% certain and it ran for about 15
> years before being replaced with newer equipment.
>
> 73, Doug Reed, N0NAS.
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