[Amps] QRO HF2000 tank coil Q question

[John Keating]

yes I took that into consideration for the calculations.

From: gudguyham [mailto:gudguyham at aol.com]
Sent: Monday, March 22, 2021 18:25 PM
To: John Keating; Peter Voelpel; Amps at contesting.com
Subject: Re: [Amps] QRO HF2000 tank coil Q question

Have you guys taken into consideration that the tank circuit in these amps only transform down to 200 ohms, not 50 ohms from the plate impedance?  After the tank circuit it passes through a 4 to 1 balun which brings it down to 50 ohms.


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On Monday, March 22, 2021, 2:05 PM, John Keating <john.keating at outlook.com> wrote:
Thanks Peter. I calculate a Q of 7 to 8 for the stock design mentioned in the previous email.

There are still a fair number of these amps in use, I wondered if others had similar experience.

I considered redesigning for higher Q but the modifications to the entire tank circuit would be extensive. Again, I wondered if anyone had done such a thing.

73, John

-----Original Message-----
From: Peter Voelpel [mailto:dj7ww at t-online.de<mailto:dj7ww at t-online.de>]
Sent: Monday, March 22, 2021 10:52 AM
To: 'John Keating'; Amps at contesting.com<mailto:Amps at contesting.com>
Subject: RE: [Amps] QRO HF2000 tank coil Q question

I used stacks of T225-2 for a mobile antenna loading coil on 40m.
Measured Q was around 400.
Toroid coils with taps, which no good idea anyway, will have much lower Q.
As part of a pi network for 160m in the 2KW out class only T400 was not
getting too hot, stacks of T300 still overheated in RTTY.

73
Peter

-----Original Message-----
From: Amps [mailto:amps-bounces at contesting.com<mailto:amps-bounces at contesting.com>] On Behalf Of John Keating
Sent: Montag, 22. März 2021 17:23
To: Amps at contesting.com<mailto:Amps at contesting.com>
Subject: [Amps] QRO HF2000 tank coil Q question

Wondering if anyone can provide the specs on the low band tank coil for a
QRO HF2000.

It appears to be a stack of two red-mix T225A-2 iron powder toroids, with a
total of 25 turns, and taps for 40M at the 7th turn, and for 80M at the 13th
turn.

Also wondering if anyone else notices how hot it gets on 160m.

73, John
AI6LY

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