[TenTec] Amplifier Question
Bob McGraw - K4TAX
RMcGraw at Blomand.net
Wed Jun 26 19:58:58 EDT 2013
The tuner is the last thing in the sequence of equipment before the signals
goes out to the antennas. I do use a 238 tuner for the coax fed antennas
and a balanced tuner for the balanced fed antennas. The input of the tuner
has the choke balun to the output of the SWR/Power meter. Since the coax
feeds to the antennas aren't necessarily at 50 ohms, which is the reason we
use a tuner, I prefer to have the choke balun in the system where the Z is
always 50 ohms and that would be on the input to the tuner.
I find the Diawa 801-HP to be a very good station instrument. I did follow
earlier posts and put a wire jumper such that it reads SWR and Peak Hold
power. The original models didn't read SWR when selected to read Peak Hold
power. There's also some mods to change a couple of time constant
parameters but I've not found that necessary. Additionally I did find
after doing the modification, but likely not related to installing the mods,
a calibration was necessary. This was easy to do for both AVG power and
Peak power as well as SWR power for all three ranges. Once calibrated using
a known value dummy load and RF voltmeter, my preferred method for power
measurement, I find that the Diawa CN801-HP has equal to or better accuracy
than my Bird 43P.
I do have additional switching which I didn't describe. There's two
transceivers plus the antenna analyzer that has to be switched to the input
of the amp along with two different tuners and a dummy load that gets
switched on the output of the amp. The objective; (a) adjust either of the
tuners using the antenna analyzer such that the input of the tuner is 50
ohms at the desired frequency. (b) adjust the amp for proper operation
without putting a signal on the air. That's where the dummy load comes in.
Once (a) and (b) are done, the amp is switched to the tuner and all is ready
to run. No further tuning needed.
Since everything prior to the output of the tuners will be operating at 50
ohms, I find that RG-8X is most adequate for up to legal limit power to 10M.
It is much easier to physically configure for various stations and the
For the stations I use a 30 amp switching supply with a distribution buss.
It handles three transceivers and other station accessories without any
My methods aren't the only way to handle multiple stations but my method
works. I don't encounter any RFI issues, any band, any mode, any frequency
up to legal limit power.
----- Original Message -----
From: "Richards" <jrichards at k8jhr.com>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Wednesday, June 26, 2013 5:06 PM
Subject: Re: [TenTec] Amplifier Question
> On 6/26/2013 7:39 AM, Bob McGraw - K4TAX wrote:
>> Basic station set-up:
>> The Omni VII output is connected direct to the amp input. Also two QSK
>> cables, RCA to RCA, are connected between the amp and transceiver.
> Er ... point taken, but you left out my
> home brew two-transceiver A/B switch which
> switches the mic, headphones, speakers, PTT,
> code key, and amp key lines between the to main
> transceivers. I am so darned pleased with it
> (at least I am now that I fixed the wiring error
> on the mic line...oops!)
> But I get your drift.
>> output of the amp goes to the input of a Diawa CN-801HP.
> OK. I recently read your review of that
> product on eHam.net and was curious if you still
> felt the same about it. Apparently you do.
> Power for the
>> CN-801HP is obtained via a separate cable connected to the +12V on the
>> Omni VII.
> Hmmm... I will have to find or make a splitter
> cable, and check the amperage, etc., as I use
> the .5 amp accessory power output on the rear
> panel to power a little fan I built to cool the
> heat sink fins. This saved me $40 on cost of
> buying the official TT fan accessory - in good
> old cheap ham tradition...
> I have one large linear power supply just for
> the transceivers and a separate same size linear
> supply just for accessories. Like money, sex,
> and good bourbon... one can never have too much
> power in the shack.
> The output of the CN-801HP goes to the input of the 238 tuner
>> using a choke balun, Wireman #8232, between the output of the Diawa and
>> the input to the tuner.
> Hmmm.... I did not see this one coming...
> I already have a choke on the patch cable running
> from the output of the tuner to the external
> remote coax switch. Is this not the best
> place for it - should I move it between the
> amp/meter and the tuner? Or can it stay where
> it is "close enough."
> I made my choke from a series of formula 31 clamp
> on ferrite beads, secured with shrink tubing,
> after reading articles by our friend Jim B, K9YC,
> and W8JI - and after corresponding with balun
> enthusiast, Rick, DJ0IP last year. I patterned
> mine after the ones sold by Palomar Engineers and
> DX-Engineering, among others.
> You think it would be better ahead of, instead
> of after the tuner?
> All other coax jumpers are RG-8X.
> My patch cables are all RG-213 (although one
> or two might be LMR-400 UF.) I figure these
> are equivalent to RG-8. N'est ce pas?
> THANKS FOR THE RECOMMENDATIONS.
> --------------------------K8JHR ----------------
>> Bob, K4TAX
>> ----- Original Message ----- From: "Richards" <jrichards at k8jhr.com>
>> To: <rmcgraw at blomand.net>; "Discussion of Ten-Tec Equipment"
>> <tentec at contesting.com>
>> Sent: Wednesday, June 26, 2013 12:38 AM
>> Subject: Re: [TenTec] Amplifier Question
>>> THANK YOU ALL for the quick and helpful answers
>>> about tuning my amp. The best bit is I am doing
>>> the right thing.
>>> I have a matchbox/tuner with a fairly reliable SWR/WATT meter
>>> beyond the amp, and I watch that power meter, along with the PEAL
>>> Power meter on the amp, for power indication, while watching the Ib
>>> Grid Meter on on the left side of the amp.
>>> I sometimes get the notion to install a separate watt meter (I built
>>> the Ten Tec 1225 SWR/WATT meter a couple of months back) but I would
>>> prefer to keep things simple - I figure every patch cable, connector,
>>> and gadget in line is a power and impedance "speed bump" and would
>>> prefer to keep it simple. But the user manual was a tad skimpy on
>>> explaining how and when to use those four little meter settings.
>>> Now supposing I changed my mind and DID want a power meter in line...
>>> are there any suggestions on what to use? I have a Daiwa 101L and the
>>> TT 1225 kit, but maybe there is a better one.
>>> So... is it worth it, and why? What would it tell me that I cannot
>>> already determine from the amp and tuner meters? I see so many of
>>> them in other guys' stations, I suppose there must be more to it than
>>> the thrill of seeing the needle move or the LEDs light up! ;-)
>>> THANKS, AGAIN.
>>> ------------------ K8JHR -------------------
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>>> TenTec at contesting.com
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