[App_rpt-users] Simulcasting with RTCM/voter

[Hayden Honeywood]

Hi All,
Thanks for all on the list who have given me a hand with getting the
RTCM/voter boards running.

I currently have 1/3 of my system installed at the sites. It's as follows:

A TX only site - running a VOTER board, latest "Chuck" firmware. 9.6MHz
OCXO replacing the onboard crystal and a 10MHz OCXO to keep the transmitter
stable all on 53MHz.

On my bench at home I have an identical setup except with a receiver in
addition. Both radios are the same, audio injected in the same spot.

I've been testing various frequency offsets to avoid the cancelling of the
signal due to the inherent propagation effects at 6 metres. I've been able
to run my bench radio into a dummy load and place it so that another radio
nearby connected to an external antenna is receiving them almost the same
(i.e. overlap).

Currently 1-2Hz sounds the best. I have been encoding tone, however there
is a very audible hum, as if the CTCSS tone from each transmitter is not in
phase. The tone is 91.5Hz. I've checked/readjusted deviation levels etc,
also checked the 9.6MHz OCXO etc but I cannot seem to null it out.

I've also tested the Simulcast Launch Delay.The main site is about 13 miles
away, so I put a value of 330 in there to represent a delay of 66uS on the
bench test radio. This makes a little bit of improvement, but not an
overall huge improvement. Does anyone have an ideas that I've missed or
more information on the usage of the Simulcast Launch delay?

Hayden
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