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Author Topic: What Makes a Rig Worth Restoring?  (Read 79176 times)
W2WDX
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Posts: 218




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« Reply #30 on: September 11, 2013, 11:46:08 AM »

If the IMD and harmonic distortion in the AF stage is so bad, how come it doesn't show in the 2 tone tests?

DSP averaging and error correction. Pure test tones, like those used on two-tone tests, are not like complex waveforms like with voice. The error correction and averaging has "less math" to perform on pure tones. It is easy for error correction to reconstruct a sine wave or other simple waveforms. However on voice, what goes in is not what always comes out. What comes out is an approximation of what the waveform should have looked like. The more complex the waveform, the more averaging and error correction is performed. In others words low-fidelity. The result on voice is corrected audio, like the difference between a low-grade MP3 file and an original CD or LP recording. This is the brilliance of DSP, you can fudge it, build cheaper, and market around the inherent drawbacks. Like the lack of access or ability to modify in meaningful ways.

Another factor is the quality of the DA and AD converters used in Ham radio. They are ... well ... the one in your basic Soundblaster card or even the audio on a motherboard type computer are of significantly higher quality. However again, a simple waveforms will pass through these unscathed. Again another reason why Flex sound good or most SDR's for that matter. Better AD/DA technology.

Since the manufacturers of these transceivers have for years been selling the idea of "communications quality audio" as a way out, that is all that we expect from them. And since it is obvious most radios are made with contesting in mind, there is no real push for audio fidelity.

For example, in a very well known top of the line transceiver there is a small chip being used to handle the microphone input. The same chip is used in my neighbors Barbie Doll walkie-talkie for the same purpose (I just fixed it for her). Many have wondered why they can't get their audio to sound perfect on their new transceiver. This cost saving design thinking is the primary culprit.

One of the reasons why the FlexRadios sound so good is because they use a more expensive and much better performing audio stage. This is why the Flex sounds the same regardless of mode BTW. Some modes show audio flaws better and some hide them. AM being one that shows the flaws very readily. This is why even the most expensive rice warmers generally never sound good on AM even if operated correctly.

With boat anchors, the audio circuits are just and only that. Audio! NO fudging, no feature sets, just audio. If you look at a push-pull plate modulated boatanchor, the modulator circuit is a basic audio amplifier like that used on a stereo system. The only real difference is the modulation transformer have a different secondary for higher impedance loads. Otherwise they are high-fidelity audio amplifiers. I have used Dynaco amplifiers as modulators. Eico converted one of its monoblock audio amplifiers, by only adding a mic stage and changing the output transformer, to make a modulator called the 730.

New radio's just can't and are not designed to perform on this level insofar as audio goes. The design criteria is for small size and feature sets, and that's it. Everything else is a compromise or even an afterthought.

DSP is a hack that allows a deep feature set that is very inexpensive to produce, nothing more. Furthermore the need for a Class A PA circuit is just a marketing game, not unlike that played on audiophiles for $20,000 audio cables. It's a non-issue issue. It's a "problem" created to satisfy the release of something "new", the ClassA PA. We never knew we needed it until they told us they had it. Does it make the radio perform better?  Not really and it runs hotter and produces less output. Sure you can argue the RF is cleaner, but so what? Does it exceed FCC regulations any better. No. Standard outputs do as well in this regard. Does it make the audio better? Certainly not. Now if  they used classA circuits throughout the entire analog audio sections then they'd have something. But alas, they use the cheapest crap they can, and talk about features instead. In the audio world we say, "Garbage in, Garbage out."

So endeth the off topic rant! Ha, ya got me started. As if us folk from New York ever have a shortage of opinions nor a willingness to express it! Smiley

Anyway, the old boatacnhors do sound great, when restored properly and aligned perfectly. (A few small mods can help also). Another reason to say a given boatanchor is worth restoring. Some sound better right out-of-the-box than others. Like the B&W 5100b, Collins KWS-1 or KW-1, Hallicrafters HT-32 or 37 or even the HT-20, the Miessner's, Collins 32V and the list goes on. Oddly the only rice warmer that I have ever heard sound like these, and only after being heavily modified is the old FT-101E.

John, W2WDX
« Last Edit: September 11, 2013, 12:50:29 PM by W2WDX » Logged

G3RZP
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Posts: 1280




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« Reply #31 on: September 11, 2013, 02:35:20 PM »

John,

Are you saying that putting two non harmonically related tones into a transceiver that has DSP will not produce tones with  no audio harmonics in the output? If so, why would it produce harmonics and IMD products  on voice?

Older, totally analogue transceivers will be innocent in this respect, but I find it hard to believe that a DSP based transceiver has such a memory...
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KG8LB
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Posts: 408




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« Reply #32 on: September 17, 2013, 09:43:32 AM »

HI all,

Here's a few I restored. It certainly is a labor of love.


A sad Collins 75A-2 Before:




Do a little of this ...




Do a little of that ...





... And you get this after! (It even got a restored cabinet!)






National NC-109 (This is a tough cabinet and faceplate to refinish. How's it look?)






My Clegg Zeus





You fix some these ....




Stick them in one of these, that you have cleaned and alodined ...




Paint and bake one of these ...




Go blind doing this ...




Put it all together ...



And you get one of these!!!




And that's just a small sampling!

Doing this is great fun, educational and rewarding. That makes it all worth it.

John, W2WDX


Oh and for you guys talking about ClassA SS rigs. Open one up and test the microphone stage. You will find THD and IMD in the tens of percent. A ClassA PA does not fix busted audio pre DSP.


 Nice stuff ! Looks like you understand the thread is not about old vs new . It is about how well this stuff has proven it's merit and just how DURABLE and useful over the long haul .
  My personal preference is to NEVER paint or refinish but to preserve function and finish .
 But that doesn't mean others should not refinish . 

    If all I had available were the late model , boring appliances I would take up knitting !
Thankfully we have a huge reserve of very durable , viable US built iron to keep us on the air for decades to come . That is all worthwhile !
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W2WDX
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Posts: 218




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« Reply #33 on: September 18, 2013, 10:56:04 PM »

I totally agree with your thinking on refinishing, with only one caveat. Research.

Particularly with military gear, or products from companies who made gear for the military regularly, documentation was an important aspect of manufacturing. And while Collins, or defunct companies like Hammarlund or Hallicrafters may not have preserved its documents, most times the military has. On certain level projects, having these documents allow me to use the same techniques and even know the formulations for paints for instance, at the time of manufacture. The methodology, or the manner, in which paints were applied is also documented well; even for specific models and even variants.

It is therefore possible to re-finish as factory new (or even in some remote cases re-fabricate accurately), and in fact better quality then the "depot" could perform on an R-390A, for example. This is because you are using manufacturing documentation, not service oriented data.

But this should only be performed after extensive research if a historical conservationism aspect is to be applied to the restoration goals.

And this is not only from a cosmetic or even "toughness" aspect, it can apply to the function of a radio. For instance, the  National RBL-5 low-band receiver has a black wrinkle coat finish over a heavy copper plating over the steel chassis. This was to fulfill the military's requirement of having low-band gear that would not interfere with other radio equipment in proximity. So the military had a specific way (or mil spec) on the method of manufacturing. It was detailed down to curves showing cool down rates and timings on baking a specific formula wrinkle coat paint.

All that being said, if the pre-work condition of original finishes for conserving adhere to the level of standards decided upon for the restoration, every attempt should be made for it to be conserved and preserved. Here's a basic example: a Clegg 22'er faceplate being conserved:






And this is a panel from a small Gates Transmitter having it's original finish conserved. The two images show before treatment and after. Incidentally, the images are relatively color accurate; there truly was that much difference before and after treatment. It's sixty years of patina and natural oxidation having been removed. The lower image is the true original color as from the factory:






It's this matter of commitment to the historical conservation I can appreciate. However if something is too far gone it may be desirable to replicate; only if a high degree of accuracy standard is maintained and researched. With the R-390A showed in my earlier post, this is how the same panel looked on this radio. More than simple conservation was necessary:


Of course all of this dependent on the level of restoration desired. If your looking to have a good functional radio to actually use daily or if you simply enjoy having something that looks and works as new. However, it should never be underestimated there may be a functional reason for what may appear to be only cosmetic. A lot of this also gleaned from the documentation, such as the case with the National RBL.

John, W2WDX
« Last Edit: September 18, 2013, 11:14:27 PM by W2WDX » Logged

KG8LB
Member

Posts: 408




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« Reply #34 on: December 17, 2013, 10:18:07 AM »

"Restore" as applied to radios etc is a very abused term . Not only is the term abused but many fine old objects have been abused by the efforts of some , would be restoration artists !

  Some stuff is so far gone that indeed there is little harm in obliterating the original "patina"


  Of course we now have varnishes that are far superior to the stuff used on Chippendale chairs ...have a go at it ! Wink
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KC2VUE
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Posts: 3




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« Reply #35 on: January 05, 2014, 12:12:06 PM »

Take the time to fix it, it will be time well spent. Doing it youself will bring a sense oF Accomplishment.   Gary
That's why I'm still working on my 1st boat anchor. I'm not all that knowledgeable when it comes to electronics but I'm hoping this boat anchor will help educate me and bring it back to it's glory. I'm doing a Gonset Communicator that I got from my first hamfest for free
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W3KFQ
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Posts: 6




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« Reply #36 on: January 15, 2014, 11:49:53 AM »

Hi

I would keep on keepin that dream and question alive...considering the current crop of amateurs  who seem not to understand the days of yesteryear and the value to ham radio that the dreams engendered.

Bobby

W3KFQ
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