CCA is declaring chapter 11 bankrupty right now, in a declining tube
transmitter market. Sounds like a neat project, must weight a lot to ship
though? I worked on a Sintronic (former Singer) transmitter in college that
was on 1430 KHz, with (4) 4-400's, two for RF, two for audio I think. I
bet it was similar.
To: <amps@contesting.com>
>Date: Fri, 22 Jan 1999 10:11:01 -0800
>From: "Ron Spencer" <n4vos@mis.net>
>Subject: [AMPS] Turns counters & am tx.
>
>I have aquired a cca 1000d am transmitter. It is in service and will be
>removed 1/22/99. It is being replaced with a new harris solid state
>it has 4- 4-400 tubes plus a extra modulation xformer and some tubes. I
>would sell Make Offer '
----------------------
To: <amps@contesting.com>
>Date: Thu, 21 Jan 1999 06:19:41 PST
>From: "Bill Murphy" <zuluhe@hotmail.com>
>Subject: [AMPS] 4cx5000
>
>Just a aquired a surplus 4cx5000 rf deck and power supply which is odd
>ball volts and frequency, looks a like a aircraft amp.
>I need to build a 7500 volts 2 amp pwr supply. What is the most suitable
>approach? Where do you get 30000 volt 2 amp diodes, and is a C filter
>suitable with this size power supply? Also what minimum C should be used
>and what roughly would the secondary volts be? Also for regulation what
>is the maximum volts that can be no load applied to this particular
>tube?
Bill,
In the Broadcast Electronics FM transmitters using a 4CX3500A, for 3.5 and
5.5 KW output VHF, I designed two variants of PS. The higher power rig used
a 3 phase FWB, and a choke input with a single shunt C. The values were
sufficent to get the ripple down -60 dB I think. Its been a long time since
I did this, so don't quote me. Maybe values like 6 Hy and 4 uF for that
model. The single phase rig, for 3500 Watts output had a resonant choke
input filter, followed by a C and then a small L-C smooting section for the
higher freq AC harmonics. Regulation was excellent for a single phase PS,
like a few hundred volts out of 4500, for no load to full load. Considering
it was constant signal (FM) operation, it was overkill, but it certainly
made it nice when you pulled the exciter drive cable and left the PA on
(class C, went into cutoff). No pegged HV meters when unloaded.
Your PS is larger than these, but the amperage is about the same. The idea
of stringing diodes on perf board can work, I would be very careful.
I used rectifiers potted in sticks made by HV Components Associates in
Howell, NJ. Another source at the time was Seimens (?). Not sure if you can
get these for cheap though. They were nice that you mounted them on a plate
and got rid of some of the heat in the stack. I used the same sticks in
both models, they were made as a half bridge in the sticks (strings of
diodes in both directions with a center common connection. The 3.5 used two
blocks, the 5.5 used three. Again, these were L input filters, so the
diodes had a lot less peak current in them than a pure C input filter.
Don't forget that your series R in the DC B+ lead will do a lot to help
protect your diodes from an amplifier arc. Also, the impedance of your pig.
Peter Dahl seems to have a variety of iron that could be suitable.
As for calculating the component values and ratings, check Terman Radio
Engineering, the Radio Handbook, the ARRL Handbook, and finally the older
copies of the Motorola diode handbook. In any case, you are going to have a
hard time running that 15 KVA of power supply on a single phase line, as
that's over 70 Amperes of AC current! Which points to 3 phase as the way to
go. Residential 3 phase circuits are hard to get aren't they?
Maybe I'm all washed up, thinking of FM while you are talking about SSB,
intermittent operation. Somebody help us here.
John
K5PRO
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