[TenTec] Scout 555: power goes down as frequency goes up

[Carlos]

Well, mistery solved.

One of the two drivers (2SC2166) is crook. At least they are cheaper than
the MRF455 finals.

A popular auction site is plagued with counterfeits, it is too risky to buy
there (I was badly burnt with 4 x VRF2933 recently). Any good source out
there ? Buying RF devices from China is like going on a picnic to a
minefield.


73,
Carlos VK1EA



On Saturday, June 1, 2019, Carlos <carlos.peco at gmail.com> wrote:
> Hi Gary,
>
> I measured the power generated in "tune" mode. I did not have a
microphone or a key with me, but the low power issue appears in both SSB
voice or with a key.
>
> QRG    PWR    I at 12.5VDC
>
> 3700   10W   5.4A
> 7200    9W   5.2A
> 14200   8W   5.0A
> 21400  0.5W  1.8A
> 28200  0.25W 1.5A
> 28700  0.2W  1.5A
>
> I don't know if this is one of the Scouts with the FET driver. Going for
a trip tomorrow, I hope to check it next weekend.
>
> I bought the radio from ebay Australia, it was a total scam. It took me a
while to fix all the issues, I even had to fit a new PTO shaft (the radio
had been dropped by someone and it was bent).
>
> 73,
> Carlos VK1EA
>
>
>
>
> On Saturday, June 1, 2019, MadScientist <dukeshifi at comcast.net> wrote:
>> Does your Scout have the FET driver transistors or the bipolar?
>>
>> Can you measure current drawn by the radio when transmitting?
>>
>> If so, check to see if the current draw on the weak bands is the same or
higher than on the strong bands.
>>
>> As it happens, the signal going through the driver stage can get
distorted (harmonic distortion) and these harmonics go into the final  but
not out the low pass filter, so all that lost signal is lost as heat in the
final and LPF.
>>
>> Gary
>>
>> Sent from my iPad
>>
>>> On May 31, 2019, at 10:29 PM, Carlos <carlos.peco at gmail.com> wrote:
>>>
>>> Hi,
>>>
>>> I'm very fortunate having several Ten-Tec radios. I use one for several
>>> weeks, then I put it aside, and use the next one for some more weeks.
>>>
>>> So I have this Scout that I have only used in 80/40, where it puts full
>>> power (slightly more in 80 meters). But I also have modules for 20/15/10
>>> and the other day I decided to check their health.
>>>
>>> Well, everything seems to be OK in RX but, to my dismay, output power
drops
>>> as you go up in frequency, up to the point of putting less than 5W in 10
>>> meters.
>>>
>>> Before I start investigating, maybe someone knows of a common issue
that I
>>> should be looking at in the first place?
>>>
>>> Many thanks in advance,
>>> Carlos VK1EA
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>>
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