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Author Topic: Looking for recommendations for Heathkit Twoer Microphone  (Read 24796 times)
KD0YMC
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« on: July 23, 2014, 11:10:52 AM »

Hi All:

Picked up a 2nd or 3rd hand Heathkit Twoer lunchbox transceiver.  It powers up, but doesn't have a microphone.  I have been searching the interweb for a replacement (OEM is about twice the price of the radio) and found a couple that might work.  Understand it requires a Hi Z microphone.  I have seen suggestions for the Shure 450 and the Kenwood MC-50.  Any other recommendations to increase the chances of finding a mic at a reasonable price?  There is also a local upcoming ham fest that I might be able to find something.  Full disclosure:  I am a new ham with limited electronics knowledge, but know enough to do some basic rewiring, etc.

Thanks!
KD0YMC
Robert
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W9GB
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« Reply #1 on: July 25, 2014, 05:15:58 PM »

The Heathkit Two'er used a Ceramic (Hi-Z, >25K ohms) microphone.
Finding the original, will be rare.

The Turner 350C, Ceramic model (Hi-Z), would be a good substitute,
that was mfg. by Turner during this same period and used on other Heath-kit radio models.

QST Vintage Radio, by John Dilks, K2TQN - June, 2013.
http://www.wj1b.com/uploads/8/4/0/9/8409204/vintage_0613_twoer.pdf
« Last Edit: July 25, 2014, 05:20:53 PM by W9GB » Logged
W8AAZ
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Posts: 379




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« Reply #2 on: July 26, 2014, 11:45:02 AM »

Probably about a sure thing that the radio used a crystal or ceramic mic when new.  Those may have a big more output than a hi Z dynamic mic into a very high impedance load like a tube grid.  Just when buying old mics, you gotta be careful that they are good or not.  Crystal mics get weak or dead just due to the crystal being delicate.  Ceramics are a bit more rugged and will withstand more abuse or not tend to just die, maybe.  Any vintage mic of that type ought to work fine if it is functional. Dunno how you can test it unless you have something like an amp or an O scope handy.  Maybe a AC voltmeter if it can read really low voltages. Like high impedance and can register a 5-50 mV signal.  Maybe a cheap amplified CB mic, as the higher output can overcome the low impedance source issue.
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G3RZP
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« Reply #3 on: July 26, 2014, 03:11:31 PM »

Sometimes, an old crystal microphone can be brought back to life with a gentle bake in an oven at 70 degrees C. But only sometimes........
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KD0YMC
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« Reply #4 on: July 28, 2014, 07:57:15 PM »

Thanks for the assistance.  I figured an original mic is about a easy to find as a unicorn.  they are pricey when you can find one.

I will continue my search.  The turner model might be my best option.  There is a local source of relatively cheap CB mics, so that might be something to try.

I would like to bring this thing back to life.  I have crystals on order and picked up some replacement tubes for the couple that are bad.  I mainly picked this up to tinker with as part of my learning process.  I don't have an ounce of technical background, so a lot of this is picked up through self study and taking stuff apart and putting it back together.  I have a relatively low investment in this, so if it doesn't work, not much lost.  Either way its a pretty cool little radio.  Your help is much appreciated and will hopefully get this thing on the air again!
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KQ6Q
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« Reply #5 on: July 31, 2014, 01:34:57 AM »

The radio will have very limited utility - AM transmit, on frequencies determined by crystals you buy.Little or no AM activity on 2m now.. You need to join a local ham club if there is one near you... I owned a Twoer - 50 years ago!
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W8AAZ
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« Reply #6 on: August 01, 2014, 03:55:49 PM »

Yep, for 2 meter AM, better get two of them working so you can give one to a local friend and have someone to talk to.  But I cannot tell you what would be a good AM freq for 2M nowadays!  Maybe you should look for a sixer.  Perhaps a bit more chance of finding someone on six to talk to on AM. When the band is open, that is.  But there are a lot more HF rigs that now have six so presumably most of them can switch over to AM.  Can't say exactly where to put an AM sig on 6M, either, although I bet it would not be at the very bottom where CW and SSB are concentrated, or too close to the FM repeater freqs up high.   Maybe google to find something about activity? 
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KD0YMC
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« Reply #7 on: August 03, 2014, 10:02:04 AM »

Thanks for the additional info.  Just tinkering with it yesterday, might be more of project than its worth...even with limited on air activity.  I am in the market for a HF rig now (studying for general), so this one just be a good winter project.  I belong to a local club, so I will check with some of the folks to see if anyone is using it these days.  Kinda got this to learn more about electronics and its a low cost way of getting hands on experience without breaking the bank.

Thanks for all the help!
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W8AAZ
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« Reply #8 on: August 03, 2014, 06:16:54 PM »

Since the Twoer or the Heath radios like it have no push to talk function, you are more flexible in the instance you can lay hands on a crystal mic that does not have that function, like some of the other small radio or tape recorder mics that are simply mics and no switching. Of course you will need to get ahold of one of those old Switchcraft connectors to fit the radio but those are not that rare or difficult as they were used for a great number of things back in the day.  Or a high impedance dynamic could work for that matter, maybe it would not have as much output as a crystal mic but still might drive the radio.  Just don't pay a lot unless it is guaranteed to be working good with full output voltage.  Not something weak or dead.  Or if you could just get a crystal element and some shielded wire, you could make your own mic in some appropriate sort of enclosure with some imagination. Perhaps functional but not pretty? A substitute till you can find a mic that appeals or a Heath mic. Look at it as an educational project even if you can't find someone to contact right off. Besides the 6 meter radio, I think they made a CB version of that basic radio.  That could be converted or maybe realigned to work on the 29 MHz. 10 meter AM freq. I understand there is activity there, and have heard something, I think.  You will need a good antenna and band opening to QSO though.
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KB2FCV
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« Reply #9 on: August 05, 2014, 10:34:00 AM »

One suggestion is to look for a "lunchbox" for sale that has the microphone.. then share it amongst your lunchboxes
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KD0YMC
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« Reply #10 on: August 05, 2014, 08:56:09 PM »

More good suggestions.  I will have to do some research on some other microphone options, including potentially building one.

I like the idea of getting a "sixer" with a mic.  simple solution, just didn't think of it!!
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W1BR
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« Reply #11 on: August 13, 2014, 10:00:39 AM »

Depending on your location, a Sixer may be more useful than the Twoer.  Sporadic E openings provide opportunities to work other AM stations on the 50.4 MHz AM calling frequency.  Two meter coverage is much more limited, unless you have local AM nets.  I used both rigs back in the early 50s. They were decent for what they were. The problem I had with both rigs was that the mike cable would open right where the cable enters the mike housing. Unfortunately the housing is sealed, and almost impossible to open for repairs.

W9GB hit on the salient points in the second post.

Pete
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