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Author Topic: Hallicrafters SX-115 selectivity design eror  (Read 44181 times)
W1BR
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« Reply #105 on: April 02, 2015, 08:02:47 AM »

[   Even if there were a change in level, the BFO has to be moved to the ***exact same relationship *** to the signal to have the same tone, so nothing changes.

73 Tom

Except that Jim also stated that the range of audible frequencies was CW beatnote range was also increased, limiting the lower frequency that is  preferred by most CW operators. It is still masking a problem, and doesn't make any sense from that perspective. Simply moving the BFO knob would have accomplished the same results.

Pete
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AC2EU
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« Reply #106 on: April 02, 2015, 08:31:20 AM »

OK, no more need to bury the horse...it's been beaten into the ground!  Roll Eyes   Grin
Bottom line, when restoring an old radio, use the best appropriate modern caps for the intended purpose.
No doubt there will be some improvement, but At the end of the day, it was still designed half a century ago.
If you want something more accurate, buy a new rig. Geeesh!
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K9AXN
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« Reply #107 on: April 02, 2015, 10:07:41 AM »

Thanks Jim,

I'm out of here.

A good day to ya

Kindest regards Jim K9AXN
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G3RZP
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« Reply #108 on: April 02, 2015, 10:51:53 AM »

>If you want something more accurate, buy a new rig.<


Maybe. I just wouldn't assume that a new rig is necessarily better than some of 30 and 40 year old ones just because it's new.....

In the same way as it is not necessarily a good idea when management decides that 'change is progress'...
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W1BR
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« Reply #109 on: April 02, 2015, 11:10:02 AM »

OK, no more need to bury the horse...it's been beaten into the ground!  Roll Eyes   Grin
Bottom line, when restoring an old radio, use the best appropriate modern caps for the intended purpose.
No doubt there will be some improvement, but At the end of the day, it was still designed half a century ago.
If you want something more accurate, buy a new rig. Geeesh!

Exactly what I suggested eons ago...

Pete
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W8JI
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« Reply #110 on: April 02, 2015, 11:18:52 AM »

OK, no more need to bury the horse...it's been beaten into the ground!  Roll Eyes   Grin
Bottom line, when restoring an old radio, use the best appropriate modern caps for the intended purpose.
No doubt there will be some improvement, but At the end of the day, it was still designed half a century ago.
If you want something more accurate, buy a new rig. Geeesh!

I thought there might be some technical basis for the claims. There is often something to be learned when something does not make sense, but perhaps not in this case.
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KG8LB
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Posts: 408




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« Reply #111 on: April 02, 2015, 01:56:32 PM »

OK, no more need to bury the horse...it's been beaten into the ground!  Roll Eyes   Grin
Bottom line, when restoring an old radio, use the best appropriate modern caps for the intended purpose.
No doubt there will be some improvement, but At the end of the day, it was still designed half a century ago.


   And could have worked better then . With available components at the time  . This was not Hallicrafter's "bargain priced" offering .

>If you want something more accurate, buy a new rig.<


Maybe. I just wouldn't assume that a new rig is necessarily better than some of 30 and 40 year old ones just because it's new.....

In the same way as it is not necessarily a good idea when management decides that 'change is progress'...

   So true !

 
« Last Edit: April 02, 2015, 01:58:47 PM by KG8LB » Logged
KM1H
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« Reply #112 on: April 04, 2015, 09:42:03 AM »

Quote
OK, no more need to bury the horse...it's been beaten into the ground!  Roll Eyes   Grin
Bottom line, when restoring an old radio, use the best appropriate modern caps for the intended purpose.
No doubt there will be some improvement, but At the end of the day, it was still designed half a century ago.
If you want something more accurate, buy a new rig. Geeesh!

I thought there might be some technical basis for the claims. There is often something to be learned when something does not make sense, but perhaps not in this case.

There was nothing wrong in 1960-61 with the SX-115 design or choice of components. This complete thread is about one persons often confused beliefs and trying to change that is in the same category of our voodoo nichrome believer who has been preaching his nonsense for over 25 years.
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KG8LB
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« Reply #113 on: April 04, 2015, 10:06:07 AM »

Aside from the fact it could and should have been better , especially considering the price . ..... Wink


   Jim's comments had more substance than the bashing that followed .

 
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KB4QAA
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« Reply #114 on: April 04, 2015, 10:55:59 AM »

Aside from the fact it could and should have been better , especially considering the price . ..... Wink
 
That was not the subject of this thread.  At all!
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KA0HCP, ex-KB4QAA Relocated to Ks. April 2019.
KM1H
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« Reply #115 on: April 04, 2015, 11:04:59 AM »

 
Quote
  Jim's comments had more substance than the bashing that followed .

Thats YOUR opinion and a few other groupies that talk but dont do the work.
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KG8LB
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« Reply #116 on: April 04, 2015, 12:30:37 PM »

Aside from the fact it could and should have been better , especially considering the price . ..... Wink
 
That was not the subject of this thread.  At all!

   Actually , that it could have been better with proper parts selection is what Jim had claimed . Jim made his points well and politely .

There were plenty of comments that were not the subject of the thread .
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W1BR
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« Reply #117 on: April 04, 2015, 12:43:44 PM »

Aside from the fact it could and should have been better , especially considering the price . ..... Wink
 
That was not the subject of this thread.  At all!

   Actually , that it could have been better with proper parts selection is what Jim had claimed . Jim made his points well and politely .

There were plenty of comments that were not the subject of the thread .

I think it was shown that the radio would have worked, as designed, when it left the factory by the info that Tom supplied. Whether a disc ceramic cap, with Z5U dielectric, would be out of tolerance 60 years later is as moot as leaving wax paper caps in place. No parts last forever.

I would not argue that is good practice to replace vintage parts with modern components that are more stable, especially when the cost is usually only pennies.

Comments of a technical nature shouldn't be taken as personal assaults.  From what I read, Jim welcomes open dialog.

Pete
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G3RZP
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« Reply #118 on: April 04, 2015, 03:03:25 PM »

I would NEVER, as a professional engineer, have tried coupling tuned circuits with ceramic capacitors unless they were NP0. I would have used silver mica, stacked mica or polystyrene - probably the latter, but the types made with multiple leads to the foils to keep the Q up.

However, the skirt selectivity with multiple tuned circuits cannot ever compare with the shape factor of a crystal or mechanical filter because the elements just don't have the Q. Add to this, the answer to the question "How long is this thing supposed to work for?"

Performance good enough 50 or more years ago may well have maintained said 'poor by today's standards' - or it may not. Although a 1938 National HRO kept in a reasonable atmosphere might well still meet its original spec, which isn't generally quite good enough for today's conditions. If one is designing for a 10 year life under commercial pressure, different considerations apply.

Prior to my retirement from a semiconductor manufacturer, the company had had at one stage a 5 transistor array. Normal price, about 80 cents in quantity. One customer was paying $250 a pop - they needed a 30 minute guaranteed life when operating at 250C ambient. And 2000 pieces a year..

Different considerations.....
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K9AXN
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« Reply #119 on: April 04, 2015, 03:17:04 PM »

Gary,

It' great that you have the courage to speak but it will never go anywhere.

It will go quiet if there's no attention.

Kindest regards Jim K9AXN

   

 
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