building a repeater out of two Kenwood TK-880

[Steve]

Hello everyone!

 

i'm looking to integrate a Kenwood TK-880-1 ver2 with a repeater controller.... I'm about to pull the trigger on a pair or 880s and just wanted to do a bit more research before i do.   On some other models like TK-805D, there is a way to open it up and solder some connections for the rx tx, ptt, tone, gnd, etc. (see link below)  I can't seem to find anything on interfacing those.... wondering if the front RJ-11 would allow a custom cable?  I'm going to most likely order a NHRC-3.1 controller so I'll have to make a custom cable anyway.  

 

Parts include:

 

Kenwood TK-880-1 ver2 40 watt (or Kenwood TK-840-1 25watt) - both inside the GMRS band.

 

NHRC-3.1 repeater controller

NHRC-Squelch controller

 

to be figured out later:

antenna tuned for GMRS

duplexer tuned for my channel

cables

 

I could also go with TK-840 - because i can also get a good deal on a pair of those. 

 

or maybe an older TK-805D because i found detailed plans on how to build the interface cable here:

http://www.repeater-builder.com/kenwood/pdfs/tk-805-wiring.pdf

 

I was looking to stay away from the 805 and 840 because the volume and ch knobs wear out, and become noisy.  The 880 has a digital volume control and more features, so i think it would last longer, and i'd get more life out of it.  plus, its a bit higher powered, not that i need that high of power anytime soon.

 

any experience connecting the 880's or 840s to a controller?  I'm leaning more towards the 880s, for a few $ more, the version 2 gives me 40 watts.  but i'm not sure i need all that power, so i hope there is a lower 10 watt option for normal use.  the 880 is hard to find details on, but i'll keep looking!

 

Steve

 

yes, i'm GMRS licensed.

[berkinet]

The antenna i'm using is:...

...CA-712EFC

Speaking of the antenna. I was curious why you chose the CA-712EFC over the CA-F72GF.

 

While there is no real great difference between the two for GMRS, I picked the F72GF for a couple of reasons others might want to consider. Although there was a little extra work cutting the antenna to length I was able to tune it spot on to our transmit frequency. Also, because I had to open it anyway, I was able to seal it up nice and tight on reassembly and I had a chance to check all the internal solder joints as they have a (somewhat undeserved) reputation for problems.

[WQYC236]

How did you guys learn how to do all of this neat stuff? I'm struggling here with all the acronyms.   

[berkinet]

How did you guys learn how to do all of this neat stuff?...

By making lots of mistakes 

[WQYC236]

I'm truly in the presence of greatness on this forum!   

[Steve]

Do yourself huge favor and slip an appropriate length of shrink tube over the middle joint on the antenna to provide a much better water seal.

That is really excellent advice. Thanks. I'll do that. The middle already had become brittle.

S

[Steve]

How did you guys learn how to do all of this neat stuff? I'm struggling here with all the acronyms.

 

Lots of research and trial and error.

[Steve]

Speaking of the antenna. I was curious why you chose the CA-712EFC over the CA-F72GF.

While there is no real great difference between the two for GMRS, I picked the F72GF for a couple of reasons others might want to consider. Although there was a little extra work cutting the antenna to length I was able to tune it spot on to our transmit frequency. Also, because I had to open it anyway, I was able to seal it up nice and tight on reassembly and I had a chance to check all the internal solder joints as they have a (somewhat undeserved) reputation for problems.

I preferred the higher gain. Plus you can open the "C" antenna up and check joints and seal them if needed.

[zap]

Lots of research and trial and error.

Well go with trial and error.

 

Like for weatherproofing connections, I much prefer Cell tape to butyl (coax seal). It's also easier to find as Ace and Tractor Supply often stock it as "Magic Tape". For line grounding, butyl is the best way to go though.

 

 

Sent from my iPhone using Tapatalk

[mainehazmt]

Learned a lot from the CB days working with a shop. But really learned it over a military career working with the local LMR shops mostly the big M....

[Steve]

https://youtu.be/W0D5bmlRx-U

 

I made some progress..... i'm keying into a dummy load for testing around the house... just need to finish mounting the controller and fans, and building out the rest of the custom cables and circuits for the utility power out alarm, and fan control relay. The idea is to have one box with everything contained that i can pull out and take home to service. Testing sounds great, no noise from power supply or tx into the controller. idle power is 15 watts draw on utility, and 40 watts on TX, and the RF tx is only around 10 watts out, im running the TX880 on low power, and i'm not sure how much power exactly, i killed my meter. But it runs very cool on TX low power. I need to get a new cross needle SWR and RF meter now.

[Steve]

and some photos

 

https://goo.gl/photos/sVnU5TNpzWXnXqFm9

[Steve]

I can't believe it has been almost 4 years since I started this build but finally, everything is done, solar, batteries, controller, custom cables, duplexer, control radio, control yagi antenna, mast, coax, etc.    half way installed, low power, antenna only at ground level, and works great.

 

photos:

https://goo.gl/photos/sVnU5TNpzWXnXqFm9

 

battery low voltage alarm:

https://www.youtube.com/watch?v=n1JL3mUtiUI

 

Dtmf channel control gmrs repeater kenwood TK-880

https://www.youtube.com/watch?v=0d06MtueMWM

[berkinet]

Very nice.

[Soladaddy]

Digging the old PC tower case. Now that you have worked out all of the bugs, are you ready to mass produce on the cheap? lol.

[osculant]

Love this writeup, checked in over the last year and glad to see it basically 'done'. I have a tk-880 and have been playing with doing exactly what you've done here with an H, like you I also ended up getting an off the shelf repeater (gr300) to play with as well. Also for what it's worth I have two Ed Fong antennas I have been using for over a year and though my use has been limited to HAM and GMRS repeaters not too far,I haven't had any problems yet. The small footprint being referred to was it's wind profile, not it's coverage area.

What power supply did you end up using?

[axorlov]

As an owner of three tk-880h (two in cars, one in house), I love this build. Unlikely I will ever build a repeater, no need for me, but if I did, that would be a reference.