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Re: [Amps] Ten-Tec Titan 425 - input SWR high

Subject: Re: [Amps] Ten-Tec Titan 425 - input SWR high
From: Prem <>
Date: Sun, 19 Oct 2014 10:38:14 -0400
List-post: <">>
Thank you Gerald.

Yes sir, I totally agree with you about the Z/vswr variance because of the
applied drive level.

The analyzer test was done to get a ball-park figure, par se.

Prior tests (inadvertently omitted in my OP) with the actual exciter
connected and driven at 50W, then 80W, also resulted in very high (>2) swr
at the input.

You are probably correct about the amp being 'NAD', however, as I'm a
newbie to the Titan 425, I wanted to hear from other experienced users of
this model - before telling my friend to use his amp "as-is" with an ATU in


On Sun, Oct 19, 2014 at 10:15 AM, <> wrote:

>  Prem, a cathode driven amplifier input impedance (and resulting vswr) is
> determined by cathode current primarily You can't get enough cathode
> current flow with a low power rf source such as the MFJ analyzer to create
> the impedance (and resulting vswr) you expect.
> To make a valid test, you need to connect a vswr meter between the
> transmitter and the input of the amplifier. Then perform the input vswr
> checks using the normal driving power that is used on the air. You can
> easily see the effects of input vswr as the driving power is reduced.
> With the data you provided, it is very likely that there is actually no
> problem.
> 73,
> Gerald K5GW
>  In a message dated 10/19/2014 8:03:04 A.M. Central Daylight Time,
> writes:
> Friends, for a long time now, the input SWR on my friend's Ten-Tec Titan
> 425 is very high (average > 2 on all bands) - when measured with a MFJ
> analyzer at the input - with a 50R dummy-load at the AMP output.
> So long, he's used an ATU between the exciter and the 425, but I'd like to
> find out if there's way to fix this SWR problem (no slug-tuning. fixed L
> and C in the i/p LPF).
> I've already checked/assessed the following:
> 1- Amp gives full o/p of 1500W pep on a DL with an ATU between the exciter
> and the amp (so, tubes should be OK ?)
> 2 - The vacuum relay contacts test 100% OK with a multi-meter continuity
> test.
> 3 - No visual or smell indication of any burns/arcing/toast - in the I/P
> LPF or in any other circuit elements.
> 4 - Band switch contacts look good. Cleaned with De-Oxit - just to be on
> the safer side.
> 5 - Ig and Ip are as per specs
> Any help/lead is appreciated.
> 73,
> Prem
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