[NLRS] 222 Beacon

[Bill Ockert - ND0B]

Good morning Doug,

Thank you for the informative note.

Hans has been working with Paul, N2EME for some modifications that include 
support for 222 as well as support for JT65 (both already done).  He is also 
going to try to implement FSK441 however is concerned he may not be able to 
jerk the PLL around fast enough.   Both JT65 and FSK441 are purely FSK so 
there are no issues with an analog component.

Because Hans is supporting 222 directly I will not be using a transverter.

I have the  OCXO and GPS options ordered so all good there.

Any of these little beasties need extra filtering to be ready for prime 
time.   I have a dual cavity filter that K0ALL set me up with at a hamfest a 
couple of years ago all tuned up and ready to go.   Through that I will be 
driving a DEMI 35W amp.   It will all get sniffed out with the spectrum 
analyzer before it gets hooked to anything other than a dummy load.

Your idea of using the U3S to drive the RF sections of a commercial FM rig 
is interesting.   I have a Mot ??? chassis around her somewhere that I spent 
considerable time trying to set up as a 6m beacon.   I got stumped because 
the output was dithered somehow and was about 30KHz wide.   I hard unhooked 
everything that could possibly be modulating it to no avail so it was 
something the micro was doing with the synthesizer directly.  DPL and 
everything else was shut off so not sure what it was.    I think that 
project will get resurrected with a U3S replacing the synthesizer and 
multiplier chain.  Thank you for the great idea!!

As I may have indicated in the earlier post I find the JTxx modes to be 
mostly useless on 6 - 222 terrestrial.   Because of the time it takes to 
transmit each message the chances of a meteor ping are very high.    If that 
happens it usually hoses several symbols which is more than the ECC can 
handle so the decode fails.   That is why I am anxious to see how Hans' 
experiments with FSK441 turn out.

There are other options out there that allow I/Q modulation with one in 
particular being of interest.   The HackRF One goes from 10MHz to 6 GHz. 
and sells for $299.  It mostly sucks on the RX side because of poor design 
but for beacon operation that does not matter.    With the IQ modulation 
ability variable strength signals or modulation variable levels and / or 
rapid FSK should not be a problem.   Biggest issue would be the need to 
create beacon software for it.    Nice winter project.

73 de Bill ND0B





-----Original Message----- 
From: Doug Reed
Sent: Monday, March 21, 2016 11:33 PM
To: Jon Platt
Cc: nlrs at mailman.qth.net
Subject: Re: [NLRS] 222 Beacon



Hi Bill.

I've been looking at the U3 kits for quite a while. I have one of the
original kits for 30M and bought a U3S most recently with his homebrew
SI5351A OCXO board and GPS receiver. I bought it mainly because of the
higher frequency range. But you do need the OCXO board if you want to
output on 6M or above for WSPR. It needs the extra stability. I think
that what I like best is the way he adjusts the TX frequency based on
GPS timing and even calculates the grid square for WSPR.

Are you using a DEMI transverter to get to 222MHz? I would guess you
might need some more filtering to keep the out-of-band crap low? The
SI5351A doesn't go to 222MHz and stability isn't that good above 12M
without the OCXO board. You might be able to use the second or third
oscillator output to replace the LO crystal in the transverter and
then you should have maybe 10e-8 accuracy for the beacon
frequency.....

I've been thinking in terms of using a U3S to drive the TX crystal
input of a surplus FM transmitter to get a fairly high-power beacon.
The FM transmitter gives filtering and higher frequencies and power.
The U3S gives stable reference frequency and all the modulation
options, within the limitation of class C amplification with the FM 
transmitter.

A couple years ago I asked Hans about adding PSK31 capability to the
U3 kit, but he replied that PSK31 requires some analog component to
the RF to achieve minimum bandwidth. He could generate something that
would decode like PSK31, but it would be wider than 31Hz. All the
other modes he supports with the U3S don't require that analog
component and work fine with class C.

<http://rudius.net/oz2m/ngnb/pi4.htm>
You might want to consider some variation of the PI4 beacon mode. It
can be done with the U3S and uses the IARU 1 minute format favored in
Europe. It used JT4 mode for beacon telemetry, CW or FSK-CW for ID,
and about 20 seconds of carrier. About the only thing it doesn't do is
multiple power levels. I considered using multiple 1 minute beacon
formats but that would probably just be more hassle to decode.

If you are using a transverter to get to 222MHz, you can use the band
outputs of the U3S to control an attenuator between the U3S and the
transverter. It is harder to get adjustable power output with an FM
transmitter. The best option I can think of would be to use an
external attenuator after the transmitter, but then you have relay
problems or need to build a high-power multi-section RF PIN
switch..... I've always wanted to have maybe two short 10dB power
steps near the end of the carrier period. It might be better to do
0dB, -20dB, -10dB, 0dB, off? Yes, I like that option.....

73, Doug Reed, N0NAS.
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