[Amps] high drive/low output QRO HF-2500
Gerald Williamson via Amps
amps at contesting.com
Mon Mar 2 16:08:52 EST 2015
Steve, do you suppose one of the two tubes is not working?
In a message dated 3/2/2015 12:44:00 P.M. Pacific Standard Time,
steve at nr4m.com writes:
Hi Carl, and others,
My apologies for taking so long to get back you everyone on this.
'Life' got in the way.
I got the amp moved over to another position and put the output into a
Driving it with an Omni 6, I got the same output on 40 as I did into an
antenna driving it with a K3.
The 4 square on 40 showed a 1.2:1 SWR and the dummy load a 1:1.
On 20 meters, I tuned it up gradually to several levels of input, doing
it by the manual. At 100 watts input from the rig, I got 1250 watts out
to the Bird wattmeter.. The input is 2100w + (2500 volts @.850 ma)
That's 59% efficiency if I don't count the 100 watts drive.
It tunes up easily, but I am not seeing the gain I once did. 40-50 watts
input used to give me 1500 easily. It's as if I lost 3-4 db of amp gain.
I used 20 meters as a second tune-up band as I don't remember using any
toroid inductors for the 20 meter tank circuit. The 40 meter toroid
part of the tank circuit looks like a 'grilled cheese sandwich', with
the plastic having heated and drooped down around the 40 meter toroid.
Regarding the 40 meter toroid: On 40 (and 20) it tunes up at the
approximate settings, per band, given in the manual, so I am not looking
at the cosmetic issues of the 40 meter toroid. It seems to have the
correct inductance to resonate with the described capacitor settings.
73 de Steve, NR4M
On 2/20/2015 01:53, Carl wrote:
> Same problem on all bands?
> ----- Original Message ----- From: "Steve Bookout" <steve at nr4m.com>
> To: <TexasRF at aol.com>; <amps at contesting.com>
> Sent: Thursday, February 19, 2015 7:40 PM
> Subject: Re: [Amps] high drive/low output QRO HF-2500
>> The K3 that is driving it shows 1.2 or 1.3 to 1 standing wave.
>> On 2/20/2015 00:31 , TexasRF at aol.com wrote:
>>> 90W drive; how much reflected?
>>> In a message dated 2/19/2015 5:22:23 P.M. Central Standard Time,
>>> steve at nr4m.com writes:
>>> Hello all,
>>> Took a QRO HF-2500 out of storage and put it on my 40 meter mult
>>> Tuned by the book (because I never can remember how to tune this
>>> without the book...) and the output is low at about 1050 watts.
>>> is with about 90 watts of drive. When last used it was used on 15
>>> but always got plenty of power out. Efficiency looks fine at
>>> about 62%
>>> (700ma @ 2400 volts)
>>> As I recall, this amp used to drive full output with 35, or so,
>>> Power doesn't drift, and tunes up easy. It's just acting more
>>> like an
>>> SB-220 than the amp it is.
>>> Plate and load cap settings appear correct per the manual.
>>> 73 de Steve, NR4M
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>>> Amps at contesting.com
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73 de Steve, NR4M
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