[Elecraft] Output power being eaten

[Dave]

I think in today’s technology, any amp recommending to run the radio at full power and expecting the ALC to protect the amp is a joke. It may not be fast enough to protect the LDMOS device. 

SPE America has a history of pointing the finger at the radio having a power overshoot as the cause of LDMOS failures. Why did SPE now come out with a version 3 of the amp which redesigns the LDMOS input to help protect against accidental overdrive.? 

Why run a radio at full power if you have a radio that can be adjusted to the proper drive level per band? 

Dave wo2x

Sent from my waxed string and tin cans. 

> On Dec 31, 2021, at 11:51 PM, Bill Frantz <frantz at pwpconsult.com> wrote:
> 
> After reading all the comments on this thread, I think that Skip, K6DWG and Bob, K4TAX have the best theory of what happened. Careful reading of the SPE 1.3K manual indicates that the power output of the amp is sampled between the amp and the internal tuner and that the recommended tune power is 30W.
> 
> So the idea that the tuner could have gotten into a state where it ate the output power is at least credible. I would expect a KW dissipated in the tuner to have damaged it, but fortunately that does not seem to have happened.
> 
> The manual strongly recommends setting the exciter radio (my K3) to maximum power output and trusting the ALC to set the correct drive power. Many here, including me, will disagree. However, as a result of this recommendation, the manuel doesn't really address the drive power issue.
> 
> Please note that the antenna is driven through coax and not open wire or ladder line, so theories based on those feed lines don't apply.
> 
> Thanks to everyone who replied. This list is a wonderful resource.
> 
> 73 Bill AE6JV
> 
>> On 12/27/21 at 2:48 PM, frantz at pwpconsult.com (Bill Frantz) wrote:
>> 
>> I didn't have a good night in the K1USN Slow Speed Test. I started
>> more-or-less on time and tried to answer CQs. None of the stations I tried
>> could hear me. My SPE 1.3K amp said I was putting out about a kilowatt,
>> although the antenna tuning on my normally low SWR 40M dipole needed to be
>> redone. I was receiving many stations, at normal levels.
>> 
>> After a few minutes, I started searching for causes, since operators calling CQ weren't hearing me and sending CQ again. Some of these operators had worked other stations, so I knew their radios were basically working. I tried maybe a half a dozen stations.
>> 
>> Finally, in desperation, I raised the tune power in my K3 exciter to 15W
>> and retuned the dipole yet again. Things started working and I managed to
>> check into the Elecraft 40M CW net via KD5ONS in OR at 0050z. With only 5
>> minutes in the contest left, I managed QSOs with W6SX and VE5MX. Thanks to
>> both of them.
>> 
>> My current theory about what was happening is that ice on the antenna was
>> eating transmit power, although receive seemed normal. Does ice seem a
>> reasonable explanation? What else could be the cause? I'd love to come up
>> with a believable answer. Even more so, avoid the situation in the future.
>> 
>> 73 Bill AE6JV
> 
> -----------------------------------------------------------------------
> Bill Frantz        | When all else fails:      | Periwinkle
> (408)348-7900      | Voice and CW.             | 150 Rivermead Rd #235
> www.pwpconsult.com |                           | Peterborough, NH 03458
> 
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