[Milsurplus] TS-234A/UP

[Bob kb8tq]

Hi

Not at all surprising for resistors not targeted at HF. Actually pretty good.

Modulator likely puts out a pulse in the “below 1 MHz” range.

Bob

> On Aug 18, 2026, at 2:58 PM, Francesco Ledda via Milsurplus <milsurplus at mailman.qth.net> wrote:
> 
> Here is  S11.  
>  
> @30 MHz 48.9+j21.35
> @15MHz 44.6+j9.3
> @ 5MHz 44.5+j1.9
> @300kHz 47.4+-j0.57
>  
> From: Jim Whartenby <old_radio at aol.com <mailto:old_radio at aol.com>> 
> Sent: Tuesday, August 18, 2026 12:52 PM
> To: Francesco Ledda <k5urg at yahoo.com <mailto:k5urg at yahoo.com>>
> Cc: milsurplus at mailman.qth.net <mailto:milsurplus at mailman.qth.net>
> Subject: Re: [Milsurplus] TS-234A/UP
>  
> Francesco
> I wonder how non-inductive the resistors actually are?  This would limit the upper frequency that one can safely use.  I believe what limits the upper frequency of most dummy loads is actually the detector network used to measure input power.  
> Do you have a tiny VNA for testing the resistor network?
> Jim
>  
> Logic is a systematic method of coming to the wrong conclusion with confidence.  Murphy
>  
>  
> On Tuesday, August 18, 2026 at 11:50:30 AM CDT, Francesco Ledda <k5urg at yahoo.com <mailto:k5urg at yahoo.com>> wrote:
>>  
>> Well, my TS-234A is indeed 50 ohm! It has 4 large 200 ohm resistors. There are no signs of manumission and looks original.  I am as puzzled as you probably will be. If interested, I can forward a picture of the inside. 
>>  
>> Best, Francesco K5URG
>> Sent from my iPad
>> 
>> 
>>> On Aug 17, 2026, at 19:15, Jim Whartenby via Milsurplus <milsurplus at mailman.qth.net <mailto:milsurplus at mailman.qth.net>> wrote:
>>> 
>>> 
>>> 16 ohms is 1/3 of 50 ohms so it might be possible that there are 3 each 50 ohm @ 425 watt elements in parallel.
>>> So it might still be useable as a standard 50 ohm load at reduced power.
>>> Jim
>>>  
>>> Logic is a systematic method of coming to the wrong conclusion with confidence.  Murphy
>>>  
>>>  
>>> On Monday, August 17, 2026 at 03:58:47 PM CDT, frledda at att.net <mailto:frledda at att.net> <frledda at att.net <mailto:frledda at att.net>> wrote:
>>>>  
>>>> Thank you, all!
>>>> 
>>>>  
>>>> 
>>>> From: milsurplus-bounces at mailman.qth.net <mailto:milsurplus-bounces at mailman.qth.net> <milsurplus-bounces at mailman.qth.net <mailto:milsurplus-bounces at mailman.qth.net>> On Behalf Of hwhall--- via Milsurplus
>>>> Sent: Monday, August 17, 2026 3:51 PM
>>>> To: k5urg at yahoo.com <mailto:k5urg at yahoo.com>; milsurplus at mailman.qth.net <mailto:milsurplus at mailman.qth.net>
>>>> Subject: Re: [Milsurplus] TS-234A/UP
>>>> 
>>>>  
>>>> 
>>>> Can we post images here? Let's see.
>>>> 
>>>>  
>>>> 
>>>> Wayne
>>>> 
>>>> WB4OGM
>>>> 
>>>>  
>>>> 
>>>> On Monday, August 17, 2026 at 02:14:20 PM MDT, k5urg at yahoo.com <mailto:k5urg at yahoo.com> <k5urg at yahoo.com <mailto:k5urg at yahoo.com>> wrote:
>>>> 
>>>>>  
>>>>> 
>>>>> Hi All,
>>>>> 
>>>>>  
>>>>> 
>>>>> I have here a dummy load labeled TS-234A/UP.  It says 1275W, but does not specify the frequency range.  
>>>>> 
>>>>>  
>>>>> 
>>>>> Does anybody have a spec of such thing that can share with me?
>>>>> 
>>>>>  
>>>>> 
>>>>> Thank you!
>>>>> 
>>>>>  
>>>>> 
>>>>> Best, Francesco K5URG
>>>>> 
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