AN762 amp from CCI

Discussion:

AN762 amp from CCI

(too old to reply)

Michael

2004-11-06 18:29:52 UTC

Hi,

I built the AN762 amp along with 6 low pass filters with parts bought from
Communication Concepts.

The amp itself (180W version) works fine and can easily produce 180W with 5W
input.

Now to the problem and question:

I wanted to put it in a good solid case with the filters, a RX/TX relay (8A
240V Omron relay also bought at CCI) a manual switch for the filters and the
filters.
I also found a good heat sink for the PA.

I connected all parts with short runs of RG-58, but a lot of the power seems
to get lost in this system. If I'm lucky I can get 100W out. Even if I
bypass the filters. Is RG58 a bad choice for the internal wirering? Is the
manual switch a bad choice?
What special things should I address for optimum perfomance?

In my case the PA is placed on the back panel direcly mounted on the heat
sink. I made a rectangular hole in the back for the PA board.
The input and output connectors are also on the back panel. The filters are
mounted at the bottom of the box and connected to a band switch mounted on
the front panel. Behind the filters and in front of the PA is the RX/TX
relay cirucuit.

73
de
Michael
OZ8AGB

Tim Wescott

2004-11-06 19:31:48 UTC

Permalink

Post by Michael
Hi,
I built the AN762 amp along with 6 low pass filters with parts bought from
Communication Concepts.
The amp itself (180W version) works fine and can easily produce 180W with 5W
input.
I wanted to put it in a good solid case with the filters, a RX/TX relay (8A
240V Omron relay also bought at CCI) a manual switch for the filters and the
filters.
I also found a good heat sink for the PA.
I connected all parts with short runs of RG-58, but a lot of the power seems
to get lost in this system. If I'm lucky I can get 100W out. Even if I
bypass the filters. Is RG58 a bad choice for the internal wirering? Is the
manual switch a bad choice?
What special things should I address for optimum perfomance?
In my case the PA is placed on the back panel direcly mounted on the heat
sink. I made a rectangular hole in the back for the PA board.
The input and output connectors are also on the back panel. The filters are
mounted at the bottom of the box and connected to a band switch mounted on
the front panel. Behind the filters and in front of the PA is the RX/TX
relay cirucuit.
73
de
Michael
OZ8AGB

Is this HF? RG-58 should be fine. RG-174 should be fine for that
matter, if this is HF or even VHF. I would suspect that you either have
one defective component, a poorly attached connector, or a damaged cable.

Assuming that it's linear you could just put 5W in, let it run into a
solid dummy load for a while, then feel around the input path for the
hot thing. If you're losing 2 watts to one component you'll be able to
feel it.

If you can you may want to feed the amp it's 5W directly and see if it
still gives 180W. If it were me and I was desperate I'd yank the amp
out of the case, make sure it was doing 180W on the bench, then put it
back in the case checking at every step. So I'd verify 180W with it
just bolted in, then verify power through the filters (accepting a bit
of loss), then verify power with the case's connectors, etc., until I
either found the problem or had my completed amp.

--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Michael

2004-11-06 21:24:17 UTC

Permalink

Hi Tim,

Yes it is a linear PA for 1-30MHz.

I did disconnect all filters etc. and just connected input and output
directly with 2 short pieces of coax. That worked fine. 180W clean output.
I'll try out your suggestion and recheck every path and see if I find the
"bug".
Thanks!

73
Michael

Post by Michael
Hi,
I built the AN762 amp along with 6 low pass filters with parts bought
from Communication Concepts.
The amp itself (180W version) works fine and can easily produce 180W with
5W input.
I wanted to put it in a good solid case with the filters, a RX/TX relay
(8A 240V Omron relay also bought at CCI) a manual switch for the filters
and the filters.
I also found a good heat sink for the PA.
I connected all parts with short runs of RG-58, but a lot of the power
seems to get lost in this system. If I'm lucky I can get 100W out. Even
if I bypass the filters. Is RG58 a bad choice for the internal wirering?
Is the manual switch a bad choice?
What special things should I address for optimum perfomance?
In my case the PA is placed on the back panel direcly mounted on the heat
sink. I made a rectangular hole in the back for the PA board.
The input and output connectors are also on the back panel. The filters
are mounted at the bottom of the box and connected to a band switch
mounted on the front panel. Behind the filters and in front of the PA is
the RX/TX relay cirucuit.
73
de
Michael
OZ8AGB

Is this HF? RG-58 should be fine. RG-174 should be fine for that matter,
if this is HF or even VHF. I would suspect that you either have one
defective component, a poorly attached connector, or a damaged cable.
Assuming that it's linear you could just put 5W in, let it run into a
solid dummy load for a while, then feel around the input path for the hot
thing. If you're losing 2 watts to one component you'll be able to feel
it.
If you can you may want to feed the amp it's 5W directly and see if it
still gives 180W. If it were me and I was desperate I'd yank the amp out
of the case, make sure it was doing 180W on the bench, then put it back in
the case checking at every step. So I'd verify 180W with it just bolted
in, then verify power through the filters (accepting a bit of loss), then
verify power with the case's connectors, etc., until I either found the
problem or had my completed amp.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Michael

2004-11-06 21:24:35 UTC

Permalink

Post by Michael
Hi,
I built the AN762 amp along with 6 low pass filters with parts bought
from Communication Concepts.
The amp itself (180W version) works fine and can easily produce 180W with
5W input.
I wanted to put it in a good solid case with the filters, a RX/TX relay
(8A 240V Omron relay also bought at CCI) a manual switch for the filters
and the filters.
I also found a good heat sink for the PA.
I connected all parts with short runs of RG-58, but a lot of the power
seems to get lost in this system. If I'm lucky I can get 100W out. Even
if I bypass the filters. Is RG58 a bad choice for the internal wirering?
Is the manual switch a bad choice?
What special things should I address for optimum perfomance?
In my case the PA is placed on the back panel direcly mounted on the heat
sink. I made a rectangular hole in the back for the PA board.
The input and output connectors are also on the back panel. The filters
are mounted at the bottom of the box and connected to a band switch
mounted on the front panel. Behind the filters and in front of the PA is
the RX/TX relay cirucuit.
73
de
Michael
OZ8AGB

Is this HF? RG-58 should be fine. RG-174 should be fine for that matter,
if this is HF or even VHF. I would suspect that you either have one
defective component, a poorly attached connector, or a damaged cable.
Assuming that it's linear you could just put 5W in, let it run into a
solid dummy load for a while, then feel around the input path for the hot
thing. If you're losing 2 watts to one component you'll be able to feel
it.
If you can you may want to feed the amp it's 5W directly and see if it
still gives 180W. If it were me and I was desperate I'd yank the amp out
of the case, make sure it was doing 180W on the bench, then put it back in
the case checking at every step. So I'd verify 180W with it just bolted
in, then verify power through the filters (accepting a bit of loss), then
verify power with the case's connectors, etc., until I either found the
problem or had my completed amp.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

JGBOYLES

2004-11-06 22:44:03 UTC

Permalink

Post by Michael
I built the AN762 amp along with 6 low pass filters with parts bought from
Communication Concepts.

Hi Michael, Just some thoughts on your problems with the AN762.

Post by Michael
I connected all parts with short runs of RG-58, but a lot of the power seems
to get lost in this system. If I'm lucky I can get 100W out.

The short runs of RG-58 should not produce any noticeable loss. I would look
at Tx/Rx relay and the filter bandswitch.
Another thing to consider is how you determined the power gain of the PA
before and after you put it in the enclosure. Make sure all the measurement
parameters (frequency ect.) are exactly the same.
Another thing to remember is that the circuit board is the only thing that
has a power gain. All the cabling, switches, and relays will have some loss.
If you are losing 80 watts, it is probably in one section, and it should get
pretty hot. Of course the circuit board will get hot, it does in normal
operation. Look for some of the stuff you added getting hot. Also does the
circuit board get hotter now than it did before you enclosed it?

73 Gary N4AST

Joe Rocci

2004-11-07 10:36:42 UTC

Permalink

If the filter bank is on the rear panel and the filter switch is on the
front panel, it sure sounds to me like that long, circuitous path could be
the problem. I'd try eliminating the filter switching and see if the
performance returns to normal. Also be sure that whatever surface the
connectors are mounted on have a very good and short ground path back to
appropriate place on the board.

Joe
W3JDR

Michael

2004-11-07 19:19:11 UTC

Permalink

Thank you all!

I think I had a bad coax. During my bug finding I changed a couple of cables
and now 180W clean on all bands.

Thanks again!

Vy 73
de
Michael
OZ8AGB

Post by Joe Rocci
If the filter bank is on the rear panel and the filter switch is on the
front panel, it sure sounds to me like that long, circuitous path could be
the problem. I'd try eliminating the filter switching and see if the
performance returns to normal. Also be sure that whatever surface the
connectors are mounted on have a very good and short ground path back to
appropriate place on the board.
Joe
W3JDR

Post by Michael
Hi,
I built the AN762 amp along with 6 low pass filters with parts bought from
Communication Concepts.
The amp itself (180W version) works fine and can easily produce 180W with

Post by Michael
input.
I wanted to put it in a good solid case with the filters, a RX/TX relay

(8A

Post by Michael
240V Omron relay also bought at CCI) a manual switch for the filters and

the

Post by Michael
filters.
I also found a good heat sink for the PA.
I connected all parts with short runs of RG-58, but a lot of the power

seems

Post by Michael
to get lost in this system. If I'm lucky I can get 100W out. Even if I
bypass the filters. Is RG58 a bad choice for the internal wirering? Is the
manual switch a bad choice?
What special things should I address for optimum perfomance?
In my case the PA is placed on the back panel direcly mounted on the heat
sink. I made a rectangular hole in the back for the PA board.
The input and output connectors are also on the back panel. The filters

are

Post by Michael
mounted at the bottom of the box and connected to a band switch mounted on
the front panel. Behind the filters and in front of the PA is the RX/TX
relay cirucuit.
73
de
Michael
OZ8AGB

Hamish Moffatt

2004-11-10 12:46:12 UTC

Permalink

Post by Michael
Thank you all!
I think I had a bad coax. During my bug finding I changed a couple of cables
and now 180W clean on all bands.
Thanks again!
Vy 73
de
Michael
OZ8AGB

Hi Michael,

Do you have any photos of your amplifier? I am building an amplifier
based on the AN758 kit and filters from CCI.. 300W from a 48V supply. I
am looking for ideas for mounting the boards in the box etc.

73
Hamish VK3SB