[Elecraft] Roofing Filter Usage

[Jack Smith]

Racal's RA-17 was an up-converting receiver, with a first IF at 40 MHz. 
However, the 40 MHz IF filter was wideband, with the real selectivity 
applied at 1.6 MHz and 100 KHz. With the Wadley Loop tuning system, it 
was an extremely advanced design for 1955, all done with vacuum tubes, 
of course.

Jack K8ZOA

On 10/29/2010 8:57 AM, Bob W7AVK wrote:
> Bill and group - Can't say it was first, but has to be the first US
> designed and produced ham rigs to use up conversion.   The DRAKE TR-7
> has no RF Amplifier and uses a diode ring "up converter" to 43 mhz as
> the first IF.  The design was in the late 60s, early 70s.  Bob Drake and
> his company have always been know for innovative design.   In those days
> the term "Roofing Filter" hadn't be coined by the marketing types and
> the TR-7 has only one fixed filter at the high IF.     BTW - The TR-7
> second IF with the switchable mode filters is at 8.2 MHz.
>
> 73  Bob  W7AVK
>
>
>
>
> On 10/29/2010 4:45 AM, Bill W4ZV wrote:
>> Geoffrey Mackenzie-Kennedy wrote:
>>> With respect Ron, as far as I know the term "Roofing Filter" was in use
>>> many
>>> years before up-conversion superhet receivers with a fist IF at VHF
>>> started
>>> to appear in the market.
>>>
>> Correct Geoff.  The first up-conversion ham rigs were introduced in the
>> early 1980s (TS-930S I believe).  The Japanese manufacturers got the idea
>> that everyone wanted general coverage in their receivers, which then
>> required up-conversion and an IF at VHF.  Rob Sherwood had been marketing
>> his 600 Hz "roofing filter" mod for the down-conversion Drake R4C several
>> years before that, and as you said the term had already been in use many
>> years prior.
>>
>> 73,  Bill
>>
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