Link radios page

This page is all about modifying radio equipment for a better way to pass signals for long-distance links and other uses, starting with the COR/Audio board. If any of the drawings are not clear a better copy is available for a modest cost of handling.

My COR board project:

COR/Audio board Ver. 5.3 with a browser

COR/Audio board Ver. 5.3 in pdf

COR/Audio board Ver. 6.5 in pdf

COR/Audio board Ver. 6.5 Notes on parts placement

COR/Audio board Ver. 6.5 Schematic

Component side Ver. 6.5 Layout

Solder side Ver. 6.5 Layout

Motorola Mitrek area - Lot's of information

Most of these documents are in PDF for easy viewing with any O/S. Also, some of them are large in size:

Mitrek conversion to Repeater or link in PDF

Frequency options in PDF

Details on the antenna ports in PDF

Spec sheet on RG-405 coax Beldon part number of 1671A

Preselector repair in PDF

Operation manual in PDF

Motorola Micor area - Lot's of information (including Spectra-Tac)

Micor transmitter for repeater service in PDF

Transmitter supplement for the above in PDF

SRG Interface diagram for above(mobile)unit

Compa station Transmitter supplement for the above in PDF

Micor receiver conversation in PDF

Spectra-TAC Interface SRG version block and level

Spectra-Tac supplement (goes with above document)in PDF

Spectra-Tac PL Module (goes with above document) in PDF

Micor squelch theory discussion in PDF

COR board version 5.4 for Micor Spectra-Tac downlink in PDF

Repeater equipment

Evaluation for the LDG electronics voter.

IDer boards Documentation by Karl Shoemaker

Repeater operation General information

Other equipment

MX-350 Portable radio for UHF links

MX-350 channel element OEM information - just the one page

Maxar radio Just a few notes

GE for repeater operation in PDF

Audio Standards Flat, conventional and compressed audio-level standards

Microphone discussion by Tomi Engdahl

Direct F.M. a Midland 13-509, or most any transmitter

Midland 13-509 Full story on F.M. and repeater conversions for 1 1/4 meters

Wilson 1 1/4 meter radio For the model T2202SM HT.

Johnson PPL6060 Stability notes

Kenwood mobile radio evaluation and notes for the TM-V71A radio

FCU Fan Cooling Unit used to cool transmitters used in some SRG projects

I.C.M. Past services (closed now)

T600 FRS radio

RVS-8 A voter that was used a few years ago for SRG

JPS A voter that is used for SRG

When performing FM conversions to PM equipment this modulation index chart may be helpful which can be viewed here here

Occasionally, the Author needs to measure receiver sensitivity (20 db quieting method) in a location other than in front of the equipment. Hauling an expensive AC volt meter up the tower is not the first choice. Recently, he found a low-cost self contained sound level meter (SLM) from the vintage days of Radio Shack. It has a built-in battery. It has 10-db step sensitivity which is perfect for this type of measurements. With a simple (temp-prototype) modification a higher impedance input was added across the "cal" pot. This did not affect the other functions of this meter.


For now a set of pins where installed which connects directly to the Micor TAC receiver service module as shown here.


Calibration for this unit was confirmed with a HP 3555 meter. Both meters where clipped in parallel for this task.


A note about the documents; recently they are starting to be converted to PDF for a couple reasons; this solves the issue with html pages (with images) being displayed on various browsers (with other variables) and generally is smaller in file size. This is especially true for a MS-Word document (with images) compared to the size of the same document in PDF. PDFs are easy to download to your PC for later viewing.

Note: Many of these projects are in the R-n-D stage, therefore, are subject to change and improvement without notice. They are intended to get the experienced builder in the right direction and not necessarily for the beginner. Tip: Some are PDF's therefore, to save time you can right click on the link and "save as" to your PC for local (and faster) viewing.

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