Title: Strange nummbers in Switches bias
Post by: YL3CAAE on 20. May 2018, 20:22:29
Hello.
I got strange nummbers in Bias switch B1
1) Turned on RX, volts on all bands exept 20/30m
2) Turned on RX volts on 20/30m
3) Oms when switched off
If i understand correctly B1 need be same as B2,B3, B4
73
Ilvars
Yl3CAAE
|
Title: Re:Strange nummbers in Switches bias
Post by: DJ3FV on 21. May 2018, 05:59:32
Hello Ilvars,
it would be helpful if you can give us some details about the rig or version of the mcHF you own and talking about.
73, Uwe |
Title: Re:Strange nummbers in Switches bias
Post by: YL3CAAE on 21. May 2018, 07:48:50
Hello,
i got v6 board.
73
Ilvars
Yl3CAAE |
Title: Re:Strange nummbers in Switches bias
Post by: peter_77 on 21. May 2018, 08:25:01
Its all documented in the original circuit diagram for the 0.6 version:
http://www.m0nka.co.uk/wp-content/uploads/2016/03/mcHF_rf-1.pdf
If you like to improve the BIAS network a bit you can change some values and use the BIAS modification from IZ6MAF:
https://www.amateurfunk-sulingen.de/forum/index.php?board=15;action=display;threadid=910;start=30 (https://www.amateurfunk-sulingen.de/forum/index.php?board=15;action=display;threadid=910;start=30) |
Title: Re:Strange nummbers in Switches bias
Post by: YL3CAAE on 21. May 2018, 08:44:10
Hello peter,
How i understund Bias circut, on all B1 B2 B3 B4, need be same parametrs, I do not understud why resistance and volts change in B1, all reistors ( R3a R3b R3c R3d )is same size 100k on all circuts
I ask this becouse i got problem with D3 diode in Antena switch, i change it to new but mybe i got some more broken parts what need change. |
Title: Re:Strange nummbers in Switches bias
Post by: peter_77 on 21. May 2018, 09:00:48
Its a standard voltage divider circuit in the bias network. B1 should not differ from B2 to B4 of course. Its all the same.
If you have such a strange difference here you might have a problem at U1 or probably R1 or C1 and a possible solder bridge or wrong component (U1) ?!
D3 is a whole different story. Here you need to pay attention on RFC2 !
In case you put HF on it and have a bad SWR this coil can burn in seldom circumstances. So make sure you use the correct TDK coils here !
Or... do the radical change and make the relais modification to get rid of all pin diode related issues:
https://www.amateurfunk-sulingen.de/mchf-projekt/modifikationen#start (https://www.amateurfunk-sulingen.de/mchf-projekt/modifikationen#start)
(RF-04/05-H-029)
There are some photos of this modification here in the forum as well. |
Title: Re:Strange nummbers in Switches bias
Post by: YL3CAAE on 21. May 2018, 21:01:05
thanks for advise peter
i check r1 and c1 looks it`s ok, ( how i can check in board ) so i order new U1 chip.
About (RF-04/05-H-029) i need little help with D4 antiparallel diodes, i don`t understand how antiparallel diodes work? |
Title: Re:Strange nummbers in Switches bias
Post by: DF8OE on 22. May 2018, 07:21:23
If input voltages is increasing and level is getting higher than ~0.6V diodes will shorten them to ground so that no damages in preamp circuit can come up.
vy 73
Andreas |
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