[AMPS] QRO HF2500 x ALPHA89 - some experience [OK1RI]

Jiri Sanda jirka@jimaz.cz
Tue, 21 Jan 1997 15:58:41 +0100

From: 	Rich Measures[SMTP:measures@vc.net]
Sent: 	22. června 1997 16:41
To: 	John Lane; Jiri Sanda; 'amps@contesting.com'
Subject: 	Re: [AMPS] QRO HF2500 x ALPHA89 - some experience [OK1RI]

>As I am interested in the HF-2500DX, the problems with tuning on 40 and 160
>meters seem serious and fundamental.  I would be interested in any comments
>regarding good and bad points of this amp that this forum could provide. 
>Tnx    W8KX

Half of the fun with a new amplifier is fixing design problems.  If you 
fix the tank design oversights on 40m and 160m, you will learn something. 
 Is this not better than being a vegitative appliance operator?  
Remember: there is no perfect amplifier. 
- On my Web site, there is an Excel 4 worksheet for tank calculations, 
courtesy of Vince, that may be helpful.  
If you would like to discuss fixing the tank design, please feel free to 
telephone me.  
- If you succeed in fixing a HF2500, other people would surely be 
interested in how you went about it.  What would you think about writing 
a 'circuit improvements for the HF2500' article?  If the powers-that-be 
at QST magazine reject the article, you are welcome to publish it on my 
Web site if you like.  
>> 8.The PI tank is designed so that on 40m you can not tune it properly
>>there is not enough capacity on the antenna side of the PI, 

R. L. Measures, 805-386-3734, AG6K   

Hi Rich,

thanks for an offer, that is not problem, as I have written I have not intended to use this AMP on those bands anyway and I am of course able to fix it since until 1996 you and all the others have heard me on all bands always with home made AMP..... And I do have quite a colection of EU trophies and ceritficates. You might include also OK1RF, OK1ALW and from the 80's OK5R. Always the same station. I bought those AMPs since I do want to have an AMP on each band and I wanted to have rock-solid devices with tubes having dissipation within limits and beeing driven by 50W ... and not using a pair of 4-400 with TRX on 100W and the tubes giving just just a kW out like our home made stuff.

Now more comments.

Yes I do connect the transformer to 200V since our QTH is "lost in the fields" and when we key down 2.5kW + el.heating 2-3kW there is something like 205V in the "wall" !. All the critical voltages in the AMP are stabilized, the power tubes might have a problem but as all the gurus here will probably agree with me it is less dangerous for a tube to have bigger filament voltage than smaller one. (Of course best is when the filament is stabilized like in ALPHA's). Anyway SVETLANA cat. says the filament should be within 10% so .....

The reason why I put this long article on the reflector was to warn the others. And as I feel there was-is quite bit to be aware of.

73 ! Jiri       OK1RI 

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