Fw: AM Crystal filter for SB-303

[Eddy Swynar]

Hi All...

Can anyone reading this tell Larry if the SB-301 type IF filters are directly interchangeable (sp?) with those used in the newer SB-303...?

Being a gambling man, I'd say that they are---but I think Larry would appreciate better odds than that! Hi

Tnx all & vy

~73~ Eddy VE3CUI - VE3XZ




    
----- Original Message ----- 
From: Larry Robison 
To: Eddy Swynar 
Sent: Tuesday, February 27, 2001 7:43 PM
Subject: Re: AM Crystal filter for SB-303


Thanks Eddy. My address is:
 
Larry Robison
209 High Street
Huron, OH  44839-1198
 
I appreciate the info. the only thing that worries me about making the mod is that my receiver is a SB-303 and not at 300 or 301. My radio is solid state and I believe that the impedance that the filter would be designed for, would be different. I can't see to find out anywhere if the filters for the 300-301 are interchangeable with the ones for the 303.
 
I have been in contact with Inrad and they will make me 10 of them for $110 each. That's quite a gamble and I think that could be a very expensive option! My receiver has the 3.75 khz AM filter and I am almost tempted to open it up and look at what crystals are inside of it. Boy what a mistake it would be to screw that one up!!
 
Thanks Eddy!
 
Larry W9MDX


----- Original Message ----- 
  From: Eddy Swynar 
  To: Larry Robison 
  Sent: Tuesday, February 27, 2001 5:49 PM
  Subject: Re: AM Crystal filter for SB-303


  Hi Larry...

  I got all my info direct from a former engineer at Heathkit---he still had the original blue prints of the filter!

  All I did was swap the crystals---no adjustments made at all to the L/C networks therein. I used the larger SB-300 style filter, and simply mounted it to the underchassis of my '301, with a blob of silicone/RTV sealant (it takes the skinner filter cans).

  There are 6 crystals in the SSB filter---you only need four for the AM filter. The toughest part is probably dis-assembling the darn thing! You need a desk vice, and a small propane torch (or a LARGE soldering iron!).
   
  I bought my replacement crystals from JAN Crystals in Fort Myers, Florida.
   
  The total cost is probably about $60.00, or so, not taking into account the cost of the SSB filter...but then where can you find an SB-310-style wideband AM filter these days...? And if you do, for how much?!!
   
  Give me your mailing address, & I'll try & dig up the documentation for you & mail you a copy of everything therein (I recall, I even have copies of the purchasing invoices for the crystals!).
   
  Does it work? Yes,indeed---very nicely, too, I might add, especially when played alongside a second '301 with the "stock" AM filter...in fact, I SOLD my second SB-301 that had the stock AM filter in it, & kept the other one with the homebrew filter inside!
   
  ~73~ Eddy VE3CUI - VE3XZ






  ----- Original Message ----- 
    From: Larry Robison 
    To: gswynar at MAIL.DURHAM.NET 
    Sent: Monday, February 26, 2001 11:29 PM
    Subject: AM Crystal filter for SB-303


    Eddy:
     
    My name is Larry and my call is W9MDX. I recently acquired a Hath SB-303 receiver and I like it very much "except" the AM filter is too narrow. I understand that you did a mod on a SSB filter and ended up with one that was quite the ticket for AM reception. I got the information second hand. 
     
    I am curious if the filters for the 301 are the same as the ones for the 303. Since the 303 is solid state my thinking is that they may work into a different in and out impedance even though the IF frequency is the same.
     
    Second did you have to "tune" the filter once you changed the xtals? There was mention that there was a tunable coil inside and I would guess that you might have to do something with the tuning (if you're a purist) but Iwas questioning if you fond it necessary to do anything with it.
     
    Do you have any information such as a circuit diagram and possibly the new xtal frequencies?
     
    Thanks and 73
     
    Larry W9MDX

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