[Drake] TR-4 and TR-3

[Garey Barrell]

Joe -

That's probably late 1967 early 1968, so right around the time they were 
introducing the T-4XB.  I don't remember if there was a tightening of 
the "spurious" requirements by the FCC around that time or not.

73, Garey - K4OAH
Atlanta

Drake C-Line Service Manual
<http://hr99.home.mindspring.com/R-4C_Servicez/>



joe sloss wrote:

> The change to a 8 pole filter occurred about S/N 26000.  A solid state 
> audio pre-amp was added to the TR-4's about S/N 28000.
>
> Joe k7mks----- Original Message ----- From: "Garey Barrell" 
> <k4oah at mindspring.com>
> To: "Eric" <spamsink at scoot.netis.com>
> Cc: <drake at mailman.qth.net>
> Sent: Wednesday, March 09, 2005 8:30 PM
> Subject: Re: [Drake] TR-4 and TR-3
>
>
>> The main difference is the sideband filter.  The TR-3 had the 
>> "soupcan" filter which has both filters, with discrete crystals 
>> soldered together inside a single "tin" can.  They are four pole 
>> filters at 9 MHz.  The same filter was used in the early TR-4's, 
>> later changed to a pair of filters. At first the separates were 
>> probably also four pole filters, as were the 5.645 MHz filters used 
>> in the T-4X.  They switched to eight pole 5.645 MHz filters in the 
>> T-4XB and may have also changed to eight pole 9 MHz filters in the 
>> TR-4 at around the same time.
>>
>> The four pole filters are marginal with poorer carrier and unwanted 
>> sideband suppression than the eight pole units.
>>
>