Hello all, sorry for the offtopic (but these relais can be used also for a PA...). I want to build an antenna crossover switch for two radios and six antennas and I have some 30A DPDT relais (the typ
Thanks to all for the answers. The things are changed, because now I have twelve SPST W2W vacuum relais like this: http://tinyurl.com/37uv8r So, I changed my schematic to this one, with only six 30A
Thanks Tom and Karl-Arne for the informations. I know that the relais are too much, but using only the vacuum SPST would be too risky: 1500W into receiver if some failure happens... What do you sugge
Hi Tom and all, thanks for your suggestions. I tried the relay with this ugly setup with dummy load on moving contacts, using MiniVNA: http://www.hamlan.org/maco/s66_test.jpg The SWR graph is this (1
Many thanks, Larry! I found it very interesting! 73 de Guido, ik2bcp _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo
Hello All, a homebrewed two chassis 3CX3000A7 GG amp of a friend has this strange failure when switched on TX: - no more current on plate meter - 200 mA of grid current with no signal - some power ou
Thanks to everybody who answered. I think that what Dave wrote could be very probable: next weekend I will open the PA and let you know what I will find. The HV comes with a coaxial cable, but I thin
Is it possible to neutralize a grounded cathode tube PA for minimum output signal, if the Bias voltage is set to maximum available value (ex. -80V for a pair of 6JS6C) and the drive is limited to les
Hi Ron and thanks for the answer. I know that the better method is neutralize for minimum feed through of the signal with no screen and plate voltage applied (also disconnecting only the heater volta
Hi Ron, It is important that you maintain heater power because you are trying to keep the interelectrode capacitance in the tube/s at their operating values (they vary with temperature as do the tank
Thanks Chris, I was searching for a simple and easy neutralization method that doesn't require cabinet opening and wires desoldering. Thanks and 73 Guido, ik2bcp / k2bcp Il 09/05/2019 20:41, c miller
The PA of the Yaesu FL-200B that I'm restoring has a strange problem: it tunes perfectly on 15 and 10m, but on 20, 40 and 80m it doesn't tune correctly, the power is low, the current is high and ther
First of all, thanks to everybody for the answers. Here are some tips: 1) Yes, I'm using a dummy load, which has a good SWR across the bands (1.2 max on 20m, less above and below, measured on the TX
Hi Ron, here are the graphs with Return Loss and Z, plus also two markers above and below the frequency of resonance: https://drive.google.com/open?id=1SGQP9o7CZHm7UfXB0Fk31Nce3_TA_0Eo https://drive.
Finally, I found the problem: it was a capacitor in the neutralization network (between cold side of driver coils and ground) which was 44pF instead of 250pF. It is not indicated in FL-200B schematic
A friend asked to me why the pair of almost new FU728F tubes on its commercial PA goes south. It seems that, when tubes are warm, there is a short between Grid1 and Cathode on both tubes and, when th
Many thanks to everybody for all the answers. The amp is the OM4000A, so the half power is not the 200-300W which could damage the tubes. About the TX spikes, I don't know if the FTDX-5000MP which is
Thanks Joe, but the manual says that the amp protection is activated from Grid current too high... 73 de Guido, ik2bcp Il 16/09/2019 00:20, Joe Subich, W4TV ha scritto: On 2019-09-15 4:40 PM, w9bs