On 12/11/2023 12:38 PM, Victor Rosenthal wrote:
The Henry Ultra amps have pi-network input circuits for each band.
They have adjustable coils, L1-L6 on the schematic. If someone has
misadjusted them, you can see high SWR.
The 3K/8K Ultra does not have tuned inputs ... it has a pair of
1:1.56 "UNUN" and no (cathode) swamping unlike the Alpha 77 which
has a tuned tank (parallel resonant) per band. The lack of a
tuned input in the Henry places the uncompensated grid to cathode
capacitance directly across the input.
The 3K and 8K Ultra manual with schematics and parts list is here:
<http://bama.edebris.com/download/henry/3k8kultra/3K%20and%208K%20Ultra.pdf>
73,
... Joe, W4TV
On 12/11/2023 12:38 PM, Victor Rosenthal wrote:
Carl,
I understand that the SWR as shown on the meter in the transceiver is
high when the amplifier is operating, but the SWR on the line to the
antenna is normal. Is that correct?
The Henry Ultra amps have pi-network input circuits for each band. They
have adjustable coils, L1-L6 on the schematic. If someone has
misadjusted them, you can see high SWR.
Does this happen on all bands or just some of them?
73,Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco/
On 11/12/2023 18:08, Carl Braun wrote:
Hello John
I am seeing high VSWR on my 7800 when using the Henry ULTRA amp. I
don't hear or see RFI on my monitored signal but the VSWR meter is
certainly responding differently to the Henry amp than it does to my
Alpha amp. By engaging the tuner on the 7800 I can get MOST of the
Henry's VSWR down to under 1.5 or so. Placing a W2FMI line isolator
(1:1) in between the 7800 and the Henry did nothing to lessen the high
VSWR I saw coming back at the transceiver. It should be noted that
the RF console was approx. 3' from the transceiver at the time of
testing with a 25' RG-58 exciter coa from the rig to the input of the
amp.
I've pulled my dummy load out of storage and am ready to test the amp
with that. The antennas I have been using with the Henry are all flat
at their respective frequencies. I see less than 1.3:1 at 1.5KW on my
Powermaster II monitor, and on the 7800 VSWR meter, when using the
Alpha. Palomar is sending over a couple of choke kits for the radio
room and the antenna feeds. Choke kits for the TXCVR and AMP as well
as 1:1 chokes for vertical antenna feed points. As one responder
noted; Henry basically suggests you don't use the tuner in the TXCVR
to knock down any VSWR. I plan on asking Dennis Pickering about the
issue next time I have him on the phone.
More experimenting later this week as I am currently wiring in a
240VAC feed on the opposite side of the radio room so I don't have to
test the Henry consoles in close proximity of the operating position.
More updates afterward.
Carl W9LF
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From: Amps <amps-bounces@contesting.com> On Behalf Of john@kk9a.com
Sent: Wednesday, December 6, 2023 9:43 PM
To: amps@contesting.com
Subject: Re: [Amps] Starting up a NEW Henry amp
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Are you saying that the Henry is causing RFI in your transceiver? Is
this occurring with a dummy load or does you antenna feedline have CMC?
John KK9A
Carl Braun W9LF wrote?
By enabling the tuner in the rig I can knock down most of the SWR when
running the Henry's but I don't have to do that with my other amp. One
difference... I do have a longer coax run (25') from the Henry's back
to the PM II watt meter . The Alpha has a three ft (3') jumper from
the amp to the watt meter. I'm going to shorten the coax from the
Henry RF consoles to the coupler to 8' or so to see if that lessens
any of the RF coming back to the rig. I do have a W2FMI line isolator
in the line going to the amps with no visible changes. More parts are
coming like RFI kits for the amp and transceiver, a 1:1 unun for the
output of the amp and one for the base of the antenna.
Any other Suggestions?
Thanks
Carl W9LF
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