I haven't had the chance to measure it - but - it works. According to the router statistics the line attenuation has gone up by a dB and I may have lost 500kbps on my line rate, but I can now run 100 watts on 80m without any drop outs. In the past 10 watts clobbered the router.
Sunday, 16 June 2013
ADSL drop outs caused by 80m - cured ?
It took a while but I finally realized that the sporadic multiple ADSL drop outs coincided with the 80m club championship contests!! The "short - term" cure was to turn off the router during these events!!
It took even longer to find a cure. Various ferrites had no effect but by a process of elimination the pick up was on the telephone line input to the router. Interesting given that the telephone feeds in this area are buried. Though a colleague did a professional study on this a few years ago and reports that the attenuation to buried cables is less than 10db.
Finally I built the ADSL filter described by G3VMW at here
I haven't had the chance to measure it - but - it works. According to the router statistics the line attenuation has gone up by a dB and I may have lost 500kbps on my line rate, but I can now run 100 watts on 80m without any drop outs. In the past 10 watts clobbered the router.
I haven't had the chance to measure it - but - it works. According to the router statistics the line attenuation has gone up by a dB and I may have lost 500kbps on my line rate, but I can now run 100 watts on 80m without any drop outs. In the past 10 watts clobbered the router.
Friday, 14 June 2013
Power Relays for 432MHz Mast head Preamp??
HA8ET for his new masthead 144MHz preamp uses miniature power relays rather than expensive coaxial relays to save on costs. He claims to be able to run 1kW without frying the preamp. Correspondence with Gyula revealed that he hadn't tried the same technique on 432MHz !!
So can it be done? The relays he used appear to be obsolete but the RT114012 is a close equivalent. Initial tests on a rats nest lash up showed an through loss through two relays of about 1.3dB and a return loss slightly worse than 10dB - not good. !! So what happens if you at least try reasonable construction techniques?
OK - thrown together and that track probaly isn't 50 ohms. But ..............
The through loss is now down to just under 0.3dB and the return loss 15dB so its "nearly" there. The isolation to the RX port is only 18dB but that is to be expected - and there will be a second relay shorting this port during TX. A "Mk1 screwdriver short" gives an isolation of just over 40dB.
Unfortunately this is now tantalizingly close and would save having to remove two CX120 relays from a power amplifier!!!
OK - thrown together and that track probaly isn't 50 ohms. But ..............
The through loss is now down to just under 0.3dB and the return loss 15dB so its "nearly" there. The isolation to the RX port is only 18dB but that is to be expected - and there will be a second relay shorting this port during TX. A "Mk1 screwdriver short" gives an isolation of just over 40dB.
Unfortunately this is now tantalizingly close and would save having to remove two CX120 relays from a power amplifier!!!
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