Radio-Shack 900Mhz shack remote

Grundig YB-400 

Collins 89-S3 Info?


Radio-Shack 900Mhz shack remote (from cordless phone).


I hereby acknowledge and give and credit for the idea and development of this handy little setup (actually "hands-free") to N1KW.  Radio-Shack units 43-2101 (deluxe model featuring caller ID, etc.) or 43-1101 (basic model) have both been successfully used.  Original list price was well in excess of $100, but recently, their prices have been reduced to attractive levels around $50!   With minor modifications, these units are quite nice in that they allow the radio operator to stay on the air while any from the "operating position", and since they use FM, with very little decrease in audio quality. 

Disclaimer:  While the information here has been prepared with the utmost care, and is presented in good faith, it is strictly a guide to be used in conjunction with normal electronic shop practice and to be interpreted and used at your discretion.


Modifications described here are intended for use with the Icom 756 family of quality transceivers.  I'm sure you could interface the unit to Yeahoo or Kenmore equipment...but for that, you're on your own (...and you might want to keep your ferrites handy!).

No portable unit mods are required, and the modified unit still functions as a cordless, handsfree phone (but if you wish to use it in it's originally intended mode, it would be smart to first disconnect it from transceiver (or at least turn the transceiver OFF, before making that confidential call to your broker! [right Barry?]).  

When soldering to the SMD pc board, use one of those 100/140Watt Weller soldering guns...better yet, a 300Watt soldering iron with a tip suitable for copper gutter work!

Access to inside of base unit is gained by removal of stick-on rubber feet covering (qty. 4) #1 Philips screws.  Once inside, remove the pc board and antenna for access to conductor side. 


Four connections need to be made.  Rx audio from radio to (both conductors of) RJ11 connector (non-polarity sensitive), and Tx (microphone) audio to transceiver.  The point at which the mike audio (which is well isolated from Rx audio) can be picked up, is the most tricky, and is shown in the pix following.  Mike low can be picked up at unit ground (foil around edge of pc board).  Mike level is a bit high for the transmitter and should be knocked down with either a 50k - 50k voltage divider or a 100k pot (performance tests are called for).  To accommodate the four connections, plenty of room exists within the enclosure to mount a suitable  connector on the back of the unit.      

View of PCB (43-2101) with area of interest highlighted.

Pick up mike audio at west side of R6 when unit is oriented as shown.

View before reassembly.  Button the unit up, add a custom cable, from the four pin connector to the Icom 8 pin microphone connector, and performance tests to set TX audio level can begin.

Visible are:  Four pin connector and TX audio level adjustment pot installed in back of housing; dabs of RTV holding mod wires in place. 

Using the shack remote:  It takes very little time to change the microphone plug on the 756 over from desk mike to remote.  Once connectors are changed over, put on the remote headset, activate the remote by pushing the "Off Hook" green receiver button, adjust the audio levels on transceiver and remote to the desired volume, (and the transceiver VOX needs to be engaged if it was not previously)...other than that, there's not much to do except and sit back and QSO, or take a walk around the homestead if the spirit moves you!  

Please note:  While the unit is perfectly suited to, and capable of, allowing the continuation of a QSO while going QRPP or Bingo, amateur radio decorum and general courtesy dictates microphone muting to prevent "biological QRN" from tripping transmitter VOX!  


On 43-1101, mike audio point is common point of R95 and R8.  


Pictures and details to follow as they become available.


Grundig YB-400   

This synthesized, dual conversion, continuous coverage radio is a sensitive, hot little portable radio loaded with features and just about perfect for traveling.  Features include:   Dual timezone clocks/alarm, 40 station presets, good audio including even a BFO for CW and SSB listening, and FM band (stereo) coverage (strictly for local weather reports).  I have had a couple of issues with mine however...these were thankfully and successfully resolved with the advice of N1KW and help from Grundig's US technical guy Walter WB6-YXP (FB).  Contact him at Grundig USA:  800-872-2228...so all in all, I'm still quite pleased with the radio.

1.  Scratchy Volume Pot.
After about no more than six months of otherwise very satisfactory performance, the volume control started to scratch badly.  This is very disappointing and totally unacceptable for a relatively expensive product (I ask a hypothetical question:  If they used a prime volume control of sealed/permanently lubed  design, costing five times as much...OK, so maybe $ .50, would it not be worth it for the customer quality perception and satisfaction?).  Initially, Walter suggested using "some Radio-Shack tuner cleaner"... "forget it I said, I'm not going to do that again every week or maybe month!".  After a bit of checking, N1KW suggested the Deoxid D-5* product, since in addition to cleaning, it leaves behind an anti-oxidation/lubing, proprietary solution.  After calling Walter again to find out the correct procedure for opening the radio up* (you wouldn't want to hamfistedly [no pun intended] apply force in the wrong place or even wrong axis on the plastic case) to gain access to the innards, and applying a drop or two to the control ONLY, operating the control to clean and work the liquid in, the volume control has exhibited NO signs of scratchy volume control for at least 6 years! 

*The correct, non-damaging way to open the radio, is to remove the battery cover and batteries (work briskly or jot down presets as I don't know how long the memory will hold them after batteries are removed - mine did not loose its presets, but I got in, did the work, got out, reassembled and re-batteried within a few minutes), revealing two barbs and their retainers in the case halves.  Gentle lifting of the retainers with a diddle screwdriver releases the barbs and allows the splitting of the case halves for internal access.  Reassembly is pretty much opposite of disassembly, as they say. 

2.  Overheating/leaking batteries.
The radio consumes batteries at a rate that I would call surprisingly high (which is just one step under alarmingly high, but I guess there's a lot going on in its little electronic brain)...maybe that's why Grundig now includes a battery eliminator with the silver colored, more recent YB-400 PRO.  No problem, knowing is half the solution!  ...so I constructed a 9VDC 1A regulated battery eliminator for when the unit would be at home, and operated the radio off the wall.  One time however, I noticed the batteries were more than toasty warm...so another call to Walter followed and he explained that this is a known problem caused by using "foreign", that is non-Grundig, battery eliminators whose coaxial barrel connectors do not have the correct and critical dimensions*!  He further explained the reason as being critical so that the O.D. of the connector disconnects the batteries as it is plugged in, preventing the batteries and the battery eliminator from being connected in parallel.  The (alkaline) batteries hand clearly not been disconnected in my case which caused the battery eliminator to try to charge them...and they don't like that much at all!  Measuring the dimensions of the coaxial connector revealed, that indeed it was off (by a half mm...why they have so many sizes is truly beyond me).  Correcting the connector brought another long trouble-free period of operation.  

The last and most recent issue that occurred involved another battery over-heating (including leaking of the new NiMH I had installed).  The nasty corrosives which were expelled from these batteries made a mess of the battery compartment and even ate through the synthetic (probably polyurethane) varnish of the butcherblock kitchen table!!  Damn!  Needless to say the radio needed to be opened up for a thorough cleaning.  I am not certain of the exact reason for the failure to disconnect the internal batteries from the eliminator this time (even with the correctly dimensioned connector), but my best guess revolves around a slightly bent jack in the radio possibly caused by an inadvertent yank on the power cord.

*  Deoxid D-5 and other family of products are available from industrial electronic sources...but I don't believe Radio-Shack (haven't seen it there yet!). 

** Correct dimensions for the battery eliminator coaxial connector according to Grundig Technical (Walter) are:  I.D. (Neg.):  2.1mm    O.D. (Pos.):  5.5mm

Link to YB-400 Service  


Help me find:  Collins S-Line 89-S3 (Transmatch) info!  Please E-mail.   



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