[ARC5] HAs anyone tried the RF thermocouple on VHF?

[Bob kb8tq]

Hi

There are some very basic differences between a thermistor and thermocouple 
based power head. More or less, the thermistor approach “won out” many decades
ago. 

Bob

> On Sep 7, 2017, at 11:13 AM, Peter Gottlieb <kb2vtl at gmail.com> wrote:
> 
> I have a TS-147/UP which has an x-band waveguide thermistor mount but it's been decades since I had it open. 
> 
> Thermal measurement of power has been used a long time, but the specific sensor design needs to be matched to the frequency of interest. 
> 
> 
> Peter
> 
>> On Sep 7, 2017, at 9:40 AM, Scott Johnson <scottjohnson1 at cox.net> wrote:
>> 
>> Yes, but those thermocouples are nearly microscopic, and are measuring the temperature rise of a carbon film load.  There are actually two or more thermocouples, one for ambient temperature compensation, and another to measure the load temperature.  The HP 84XX series are a good example.  Thermistors based sensors are (were) used widely, and are considered reference standards.  More recently , diode type meters have become predominant, due to their high speed and ability to measure pulsed power accurately.  I use all three types, as well as directional line samplers (Bird), and even calorimetric (HP-434A) which has PLUMBING! (A pump, copper tubing, oil, tubes, high voltage, a fan; pretty much everything electrical and mechanical)  Best way to accurately measure mid-power microwave power in the late fifties! (see: http://www.radiomuseum.org/r/hewlett_pa_calorimetric_power_meter.html )
>> 
>> Regards,
>> 
>> Scott V. Johnson W7SVJ
>> 5111 E. Sharon Dr.
>> Scottsdale, AZ 85254-3636
>> H (602) 953-5779
>> C (480) 550-2358
>> scottjohnson1 at cox.net
>> scott.johnson at ieee.org
>> 
>> -----Original Message-----
>> From: Peter Gottlieb [mailto:kb2vtl at gmail.com] 
>> Sent: Thursday, September 7, 2017 6:21 AM
>> To: Scott Johnson <scottjohnson1 at cox.net>
>> Cc: Bill Cromwell <wrcromwell at gmail.com>; arc5 at mailman.qth.net
>> Subject: Re: [ARC5] HAs anyone tried the RF thermocouple on VHF?
>> 
>> But thermocouples are used in precision power measurement equipment well through microwaves. 
>> 
>> 
>> Peter
>> 
>>> On Sep 7, 2017, at 9:09 AM, Scott Johnson <scottjohnson1 at cox.net> wrote:
>>> 
>>> As a rule, RF thermocouples become too reactive at even the upper HF frequencies to be of any practical use.
>>> 
>>> Scott V. Johnson W7SVJ
>>> 5111 E. Sharon Dr.
>>> Scottsdale, AZ 85254-3636
>>> H (602) 953-5779
>>> C (480) 550-2358
>>> scottjohnson1 at cox.net
>>> scott.johnson at ieee.org
>>> 
>>> -----Original Message-----
>>> From: arc5-bounces at mailman.qth.net 
>>> [mailto:arc5-bounces at mailman.qth.net] On Behalf Of Bill Cromwell
>>> Sent: Thursday, September 7, 2017 6:06 AM
>>> To: arc5 at mailman.qth.net
>>> Subject: Re: [ARC5] HAs anyone tried the RF thermocouple on VHF?
>>> 
>>> Heh,
>>> 
>>> I still use a light bulb dummy load every once ina  while. But I have to listen on frequency with a real antenna first. Light bulbs radiate. I discovered that when I put on on a transceiver and started copying 40 meter stations! Out of curiosity I tried some QSOs with the light bulb and I got a few. Don't try that with your newfangled silicon final transmitter - even though I have done that too (and got away with it).
>>> 
>>> Of course, that us not VHF, either.
>>> 
>>> 73,
>>> 
>>> Bill  KU8H
>>> 
>>>> On 09/07/2017 08:53 AM, David Stinson wrote:
>>>> 
>>>> 
>>>> 
>>>> 
>>>> *From:*J Mcvey via ARC5, 2017 9:00 PM
>>>> *Subject:* [ARC5] HAs anyone tried the RF thermocouple on VHF?
>>>> 
>>>> 
>>>> 
>>>> Did they have an ammeter for the T-23?
>>>> 
>>>> ------------------------
>>>> 
>>>> 
>>>> 
>>>> The T-23 does not use an RF Current sensing thermocouple.
>>>> 
>>>> “By the book” tune-up uses a remote-meter test set and a
>>>> 
>>>> 50-ohm dummy load with light bulbs to indicate current.
>>>> 
>>>> 
>>>> 
>>>> 73 Dave AB5S
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
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>>> 
>>> --
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