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09 Feb 11


ATV at Dunstable Downs Boot Sale
Plans are being made to represent ATV at the summer amateur boot sale in Dunstable. Current proposal is for a fairly big open sided tent containing a number of tables.

Each table would be allocated to a local ATV repeater. i.e. TV, TZ, BH, EN, HV and maybe more. If possible we would receive each repeater and transmit to some.

Tests to see what will be received are due to be carried out in the near future and results will be reported on here.

Engineering update
Dave G8ADM visited the repeater to give it a "health check" on Saturday 29th January to check the repeater. Below is his report.

  • Updated the slide show to show the latest contacts and dx.

  • Cleaned the 13cm 13W PA filter.

  • Checked the antennas on the roof, all ok. (It was mega cold up there) Looked for the intermittently in the GB3TZ signal. found a very loose F plug in the output of the down converter. very strange, this was originally done up tightly. all seems to be well now, snow on the antenna may cause problems in the future. one day we will turn the antennas upside down which may help.

  • Investigated the tower cam audio problem. Russell suggested it might be some instability in the audio coax feed. I made a lead to put a 2K resistor in series with the audio lead at the camera end. No effect. Looked at a similar camera at home, all the cameras seem to have a square wave of a few KHz added to the audio. Why? The answer is to have a separate microphone, one day...

  • Replaced the waste bag that was getting full. (Mainly flies!)

  • Otherwise all was well...

GB3TZ now relayed
After a successful receive test earlier in the week; Dave G8ADM and Dave M0SAT visited the repeater on Friday 24th April and removed the existing 23cm antenna used to receive GB3TV.  A new 13cm receive antenna was installed in its place and new cables were fed through the roof and into the bell area where a filter and downconverter are housed.

Due to a problem with a connector the repeater was finally up and working by 21:35 and a great interference free P5 digital picture was received. Dave G8ADM also made some final adjustments to the 70cm digital receiver and the new FEC of 7/8 was set. Tz can now be selected by using the DTMF control command BB2 (the old GB3TV link selector).

"Yes that is a strange mast for an antenna..." This is what we wanted to see Checking the TZ receive capability
P5 and no interference!
Looking at Phil G8XTW via GB3TZ on rooftop monitor
Good views to horizon 70cm "TZ is where?" Still on the phone!

70cm Receive
The 70cm digital ATV input is now working properly.
Frequency: 436.00
Symbol Rate: 2.0 MS/s
FEC Ratio: 7/8
RF Bandwidth 2 MHz approx.
Antenna: Omni directional, Horizontal Polarization, 600ft ASL.
Sensing: Automatic, 2nd priority.

This 70cm receiver is overloaded and does not receive any input if the GB3HR voice repeater is active.
This is due to the closeness of GB3HR to GB3BH, HR overloads the BH receiver.
This can also be caused by nearby 70cm simplex contacts.
We have the best bandpass filter that we can get on the input but the frequencies are just too close.

So far G8ASI and G8ADM have been received on 70cm.