[TMC] GPR-92

Wed Mar 24 21:09:51 EDT 2021

    How interesting. I wonder who actually built the GPR-110 for 
MacKay. I know some of their stuff was built by Harris and some 
by Federal, maybe another company. It sounds like TMC should have 
stuck with transmitters. Both Collins and Hammarlund were 
innovative while TMC and Hallicrafters were not. It would be 
interesting to know something about the inside politics and why 
the apparent lack of follow through and refinement.

On 3/24/2021 3:59 PM, John Vendely wrote:
> The GPR-92 had a tuned 1st RF stage, more like the GPR-90RX and 
> RXD, whereas the GPR-92A had the broadband transformer-coupled 
> grounded-grid 1st RF stage similar to the basic GPR-90.  The 
> grounded grid versions were cheaper to produce but, like the 
> GPR-90, these receivers had strikingly poor image rejection and 
> intermod performance.  The GPR-92 series apparently did not 
> sell well and was discontinued after just a few years.  The 
> GPR-90RXD, however, was still listed in the 1968 TMC catalog, 
> though it seems unlikely many would have been sold at that late 
> date.  I recall hearing the same thing JP mentioned in an 
> earlier email--that the GPR-92 was not considered to be quite 
> as good as the GPR-90.
>
> TMC's next general purpose receiver design was the completely 
> solid-state GPR-10, a general coverage version of the 
> extraordinarily complex and expensive AN/URR-64 (DDR-10) 
> developed for the U.S. Navy.  Only 6 engineering prototypes 
> were built in 1968, and work on the GPR-10 was discontinued in 
> early 1970,  by which time GPR-110 development had begun.
>
> TMC seems to have bought the Mackay 3020 for resale, listing 
> them for a time in their catalog.  It may originally have 
> served as an interim offering while the GPR-110 was under 
> development.  The GPR-110 eventually made it into limited 
> production, but its complex (though interesting and 
> sophisticated) frequency synthesizer design proved unreliable.  
> As a result, TMC ended up buying back most GPR-110s.  In at 
> least one case they were obliged to replace a customer's 
> GPR-110s with purchased Mackay receivers, probably 3020s.  I do 
> not know how many GPR-110s were produced, but it can't have 
> been many.  I know of only one person who has one and, needless 
> to say, it is non-functional.
>
> 73,
>
> John K9WT
>
>
> On 3/24/2021 4:30 PM, Richard Knoppow wrote:
>> Yet another interesting TMC receiver is the GPR-100. I 
>> downloaded the instruction book our of curiosity and 
>> recognized it as the same receiver as the MacKay Marine 3020. 
>> There is a similar MacKay 3030 which looks very much the same 
>> but is probably a later model. I had thought that all MacKay 
>> Marine equipment was made by Federal Telephone, another ITT 
>> company but evidently not. I also got the instructions for the 
>> TMC GPR-110 but it seems to have been designed for general 
>> purpose rather than maritime radio use. Again, I wonder if 
>> anyone has either set and, if  you do, what your opinion of 
>> them is.
>>    A note on the GPR-92, TMC seems to have gone back to the 
>> grounded grid first RF it used in the original GPR-90. The 
>> diversity version, the GPR-90 RXD has a more conventional 
>> pentode RF plus a re-designed BFO. The reviews of the GPR-90 
>> say the BFO pulls, surprising in any "modern" receiver. I did 
>> not look at the BFO in the 92, which in general is quite 
>> different from the 90 but evidently the GG RF stage was 
>> thought to have enough advantage to go back to it. From a 
>> design standpoint the 92 is a very interesting receiver.
>>    I rather think the GPR-92 was intended to provide a house 
>> built receiver to avoid the Hammarlund SP-600 in diversity 
>> receiver systems. TMC seems to have used Hammarlund receivers 
>> modified by Northern Radio. Eventually, Hammarlund produced 
>> the -17 which has all the diversity mods except for a gain 
>> trimmer, which could be added later. I think someone at 
>> Hammarlund was just asleep at the switch.
>>     You are all aware I am sure of the Hallicrafters version 
>> of the SP-600, Didn't quite make the grade although 
>> Hallicrafters did address the problem of drift from 
>> unregulated filaments.
>>    Oh, enough meandering.
>>
>> On 3/22/2021 3:15 PM, W2HX wrote:
>>> Mine:
>>> https://w2hx.com/x/TMC%20Technical%20Materiel%20Corporation/GPR-92-SBE-2-PMO-5/GPR-92.JPG 
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: tmc-bounces at mailman.qth.net 
>>> <tmc-bounces at mailman.qth.net> On Behalf Of Richard Knoppow
>>> Sent: Sunday, March 21, 2021 4:36 PM
>>> To: tmc <TMC at mailman.qth.net>
>>> Subject: [TMC] GPR-92
>>>
>>>      Not any traffic here lately so I will drop a rock into 
>>> the pool.
>>>      I am curious about the GPR-92. Does anyone actually have 
>>> one?
>>>  From what I've read not many were built. Evidently they were 
>>> difficult to make and performance may have been partly 
>>> wishful thinking. They are so sexy looking one wants them to 
>>> be extra good but I think it was a miss rather than a hit. 
>>> There is probably stuff in the list archive but I have not 
>>> looked.
>>>
>>
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL