The AM Forum

I am interested in finding any modifications that can be made to the SX-117 hallicrafters.

Checka the latest version of the schematic Mark.  That is about all I have found. 

For what?  The 117 is pretty good as is.

Electric Radio had an article on it about a year or two ago.

I concur with JN that the SX-117 is a very good receiver as is and the only caveat is that the alignment needs to be done more carefully than a lot of vintage gear to get all of the performance that the low second IF is capable of providing.  Not many signal generators go low enough for the low IF, I used to use an HP-606 but now I find that my HP "audio" generator is more convenient.

The preselector stage is also pretty critical in its alignment.

Also, with all of this family of Halli receivers (SX-96/100/101/115/117) if one or both crystals in the 2'nd conversion oscillator have shifted slightly in frequency you will need to either replace the affected crystal (expensive) or recalculate what the new 2'nd IF frequency should be (easy).  Before measuring the frequency of the conversion oscillators make sure that they have been adjusted for proper "activity" using the procedure in the manual since this adjustment will typically slightly affect their frequency.  To calculate, use: ((the actual frequency of conversion crystal #2 minus the actual frequency of conversion crystal #1)/2) + .75 and this will give you the new target frequency for the low IF.  The BFO should also be set at this newly calculated frequency with the pitch set at zero.

If the one or both conversion crystals have drifted and you do not make allowance for this then the receiver performance is going to suffer.  I have had to slightly change the alignment frequency on my SX-101A and one of my SX-117 receivers and after proper alignment the performance is the same as the receiver with the "correct" 2'nd conversion oscillator frequencies.  In real world use although my SX-115 is the nicest looking of the bunch I cannot really tell any performance difference between it and the SX-101 or SX-117 receivers and only a slight difference with the SX-100.

  The first IF should be aligned at the average between the two conversion crystals but this IF is fairly broad so staying at 1650 should be fine.

Thanks guys for all the replies.  I found the first part of the article in ER but for some reason, the second part doesn't seem to have ever been published.  The first part says the second part will be in the January issue, but it just isn't there! ???

It's in the February 2007 issue.

The entire ER index is available on line.