[TenTec] 3.1 KHz IF Filter for 2nd IF in Omni 6

[Gary J FollettDukes HiFi]

As I recall, when one purchased the Inroad “wide” SSB filter for the first IF, one needed to adjust the BFO frequencies in order to get proper positioning of the carrier on the filter slope. I do not (yet) know the adjustment range for the BFO’s bu I am guessing that the BFO adjustments in this one must have pushed that frequency another 300 Hz, or the BFO crystal(s) were changed out.

Anyone who had spent $1000 to have custom filters made up would certainly have taken proper measures to ensure that transmitted SSB was properly generated.

I should know the answer tomorrow.

I have not looked yet, but it is POSSIBLE that the radio may have been rewired to route the TX 9 mHz IF signal through the position 2 filter. That is a lot easier to do the one might think, due to the use of diode switching to select the desired filter, so it is possible.

The first IF filter that was in the position 2 is marked “48074” and the second IF filter in position 2 is marked 48058.

Can anyone tell me if these are the numbers for the “stock” SSB filters?

I can measure them fairly easily for bandpass but it would save some time if anyone simply knew the answer to that.

I will, however, put a frequency counter on the BFO tomorrow and measure the frequencies on LSB and USB to determine what was done to make this work. As you know, without adjustment of the BFO down the filter edge, both carrier suppression and SSB suppression would suffer quite a lot.

Gary
> On Jan 9, 2016, at 9:54 PM, Paul Kraemer <elespe at lisco.com> wrote:
> 
> How is that possible?
> The lsb and usb bfo frequencies are only 3khz apart
> Paul K0UYA
> 
> -----Original Message----- From: Gary J FollettDukes HiFi
> Sent: Saturday, January 09, 2016 9:05 PM
> To: Discussion of Ten-Tec Equipment
> Subject: Re: [TenTec] 3.1 KHz IF Filter for 2nd IF in Omni 6
> 
> I bit the bullet and took the entire bottom cover off.
> 
> I found that there is also a custom 3.1 KHz filter in the number 1 position in the first IF (9 MHz)! This is also an 8 pole filter with the IF cans on board to tailor response. It is equally well made as the second IF filter is well made.
> 
> I’ll report tomorrow on how the radio sounds with quiet band conditions and also get a transmitted SSB audio report. I may have found the Omni 6 of my dreams!
> 
> I have always hated the SSB sound of the omni 6 (all variations).
> 
> I contacted the fellow from whom I got this and he informed me that the original owner of this radio had these filters custom made for a cost of over $1000. I sill do not know what company made them but they are top quality all the way.
> 
> Apparently that fellow hated the sound of the Omni 6 as much as I doubt had the resources to take corrective action.
> 
> Hopefully these filters will offer some relief as the overall design of the Omni 6 is one of my favorites over any other radio design.
> 
> It’s also on of the prettiest radios going.
> 
> Gary
> 
> 
> 
>> On Jan 9, 2016, at 8:17 PM, Mark S. Holden <mark at holden-insurance.com> wrote:
>> 
>> On 1/9/2016 8:32 PM, Gary J FollettDukes HiFi wrote:
>>> I have a 3.1 KHz bandwidth filter in one of my Omni 6+ radios. It fits perfectly into the TenTec socket and was obviously made for the en Tec. However, it looks unlike any filter I havee ever seen in ANY Ten Tec product.
>>> 
>>> It is an 8 pole filter but it also had four small IF transformers on it, presumably to tailor the passband shape.
>>> 
>>> Has anyone heard of this filter? Does any know who made it? It is too perfect to have been a home brew job. It is built on thicker board stock than that used for most Ten Tec filters.
>>> 
>>> I would assume that its intent is to improve received audio in SSB. I am going to try it in a few minutes to see what the radio sounds like compared with the others.
>>> 
>>> Gary
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>>> 
>>> 
>> I'd expect that to be a fun filter for rag chewing.
>> 
>> My Harris RF-550 rx has a 3.24khz crystal filter that's incredible for SWL.  I also installed some crystal filters intended for the Racal 6790gm in my AOR 7030+
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