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G0TEZ > YAESU 15.12.04 15:59l 57 Lines 2060 Bytes #999 (0) @ WW
BID : 659_G0TEZ
Read: GUEST DK7JY
Subj: Re: FT290 Pluses.
Path: DB0FHN<DB0FOR<DB0SIF<DB0EA<DB0ACC<DB0GOS<DB0EEO<DB0RES<ON0AR<GB7FCR<
GB7BOB<GB7HVU
Sent: 041215/0455Z @:GB7HVU.#16.GBR.EU #:61974 [Great Harwood] FBB7.00i $:659_G
From: G0TEZ@GB7HVU.#16.GBR.EU
To : YAESU@WW
G0TEZ/TPK 1.83 Msg #:659 Date:15-12-2004 Time:4:44 GMT
No, neil.
I wasn't suggesting that the 2SC1969 is run at class A as an RF PA, in fact
it is far more likely to be at Class C.
It was just that I remembered the stats from my days repairing CB, as I did
with the 2SC1941.
Some people did in fact, run their CB radios at 10W i/p which would have
been illegal even in America.
My point was, that an over sized PA transistor together with an 'anti -
fool' diode was standard on CB.
When I ran into the same thinking with the FT290, it brought a smile to my
face:-)
I have never heard of an FT 290 with a blown PA, unlike more modern rigs.
probably because it is very easy to swap the PA so no big deal.
I didn't notice anything else in the 290. It could have an anti - fool
diode for all I know but, after 25 years and literally thousands of faults,
the old "If it ain't broke, dont fix it" mantra becomes even more relevant.
I do have the manual and did read it out of interest way back.
The FT290 manual is very comprehensive. In some ways, very like the Lada
manual which someone was mentioning recently..
I am happy to say, I have never needed it.
Thank you for your reply. Ian.
>From: ZL1ANM@ZL1AB.#11.NZL.OC
>To : YAESU@WW
>
>>From: G0TEZ@GB7HVU.#16.GBR.EU
>>To : YAESU@WW
>
>>The 2SC1969 is rated at 10W in Class A. It's maximum is 15W so, if you
>>have any sort of SWR problem with your masive 2.5W O/P, you are likely to
>>notice things going wrong long before the O/P transistor blows.
>
>
>The implication here is that the 2SC1969 was being operated in Class A.
>Class A is less than 50 percent efficient, and overall stage efficiency
>is usually expected to be not much more than 25 % when output circuit
>losses are factored in.
>Your 2.5W output therefore means that the transistor was probably being
>run at close to its maximum DC input of 10W.
>
>73 de Neil, ZL1ANM
>in Auckland.
> T4 1.5à24
>
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