Portable Repeater Build

[WRMR555]

I'm gathering all of the parts and knowledge I need for a portable TK-880H/TK-880 repeater. A lot of relevant info is documented in various places on this and other forums, and especially in Steve's Building a Repeater out of Two Kenwood TK-880 thread (thanks, @Steve!). The key difference for my project is that it will be portable.

 

Why?

Because I'd like to have a repeater that I can have set up at home, or take with me for outdoor events (camping, whatever). Plus, it's a fun project!

Requirements:

• single-person deployable
• weather-resistant
• transportable in a personal vehicle (car, pickup, etc.)
• Minimum 5 mile range (more better)
• Repeater ID and TOT functions
• Nice-to-haves
  • Voice transmission of local weather watches/warnings (I saw it on this video, and it seemed cool. PI-REPEATER, I presume?)

The plan:

Build it into a Rigid box (the top one on the stack):

One of the lower boxes will house a 100 Ah portable battery set-up with solar and DC-DC charging, and will primarily live in a vehicle and serve as both an aux battery and a deployable mobile power source. But that's a build for a different forum! In any event, it will power the repeater when the repeater is mobile.

Repeater components ( = have already)

•  TK-880H Tx radio (with mic)
•  TK-880 Rx radio
•  RFS 633-6A-2N duplexer
•  (2) KCT-19 cables (for repeater controller integration)
• Repeater controller (model TBD)
• Cooling/ventilation fan
• Bulkhead connectors:
  • 12V power (Anderson Power Pole)
  • Antenna (N-female / N-female)
  • RG-45 (if using PI-REPEATER)
•  Ed Fong GMRS antenna
• 20-25' telescoping mast (painter's pole & guy lines?)
• Antenna feed coax (LMR-400-UF?)
• Internal connection cables (LMR-240?)

Initial questions

1. Any overall concerns about the current plan or components?
2. Coax: a lot of folks seem to push towards Heliax for repeaters, but I'm balancing loss against portability and cost. Thoughts on my -400 and -240 plan?
3. Repeater controller: recommendations? Again, I really like the ability for the repeater to say something like "Hurricane Watch. Flood Warning." when those things are active and I have internet access for the repeater controller, but I presume that would require using PI-REPEATER or something else that is inherently more complex than an analog, nonvolatile-memory-bearing controller. If the PI-REPEATER can be set-and-forget, great. If it's fickle (as Pis can be), then maybe something else with the Pi piggybacking the audio in?

I'm really looking forward to getting this stuff put together, and would love any thoughts or feedback.

Edited Tuesday at 12:30 AM by WRMR555
Updated on-hand inventory

[WRUE951]

my portable RV repeater built with two Maxon 8402 radios fitted into an FAT-50 Ammo can can reach 85-90 miles with a J-Pole at higher elevation.  Doesn't do so well around wooded hilly areas. These radios don't require a controller and I draw power form my RV which is on solar so the radios fit into the can nicely with lots of extra room.   The can is vented and even fitted with a fan that kicks on via a heat sense controller inside. Pretty simple arrangement.  When I park at Lake Crawley the repeater actually get a lot of use by boaters and campers and it does in other areas as well.  

[LeoG]

5 mile range may be optimistic.  Always depends on antenna height and the surrounding territory.

Otherwise sounds like a plan

[tcp2525]

6 hours ago, WRMR555 said:

I'm gathering all of the parts and knowledge I need for a portable TK-880H/TK-880 repeater. A lot of relevant info is documented in various places on this and other forums, and especially in Steve's Building a Repeater out of Two Kenwood TK-880 thread (thanks, @Steve!). The key difference for my project is that it will be portable.

 

Why?

Because I'd like to have a repeater that I can have set up at home, or take with me for outdoor events (camping, whatever). Plus, it's a fun project!

Requirements:

• single-person deployable
• weather-resistant
• transportable in a personal vehicle (car, pickup, etc.)
• Minimum 5 mile range (more better)
• Repeater ID and TOT functions
• Nice-to-haves
  • Voice transmission of local weather watches/warnings (I saw it on this video, and it seemed cool. PI-REPEATER, I presume?)

The plan:

Build it into a Rigid box (the top one on the stack):

One of the lower boxes will house a 100 Ah portable battery set-up with solar and DC-DC charging, and will primarily live in a vehicle and serve as both an aux battery and a deployable mobile power source. But that's a build for a different forum! In any event, it will power the repeater when the repeater is mobile.

Repeater components ( = have already)

•  TK-880H Tx radio (with mic)
•  TK-880 Rx radio
•  RFS 633-6A-2N duplexer
•  (2) KCT-19 cables (for repeater controller integration)
• Repeater controller (model TBD)
• Cooling/ventilation fan
• Bulkhead connectors:
  • 12V power (Anderson Power Pole)
  • Antenna (N-female / N-female)
  • RG-45 (if using PI-REPEATER)
• Ed Fong GMRS antenna
• 20-25' telescoping mast (painter's pole & guy lines?)
• Antenna feed coax (LMR-400-UF?)
• Internal connection cables (LMR-240?)

Initial questions

1. Any overall concerns about the current plan or components?
2. Coax: a lot of folks seem to push towards Heliax for repeaters, but I'm balancing loss against portability and cost. Thoughts on my -400 and -240 plan?
3. Repeater controller: recommendations? Again, I really like the ability for the repeater to say something like "Hurricane Watch. Flood Warning." when those things are active and I have internet access for the repeater controller, but I presume that would require using PI-REPEATER or something else that is inherently more complex than an analog, nonvolatile-memory-bearing controller. If the PI-REPEATER can be set-and-forget, great. If it's fickle (as Pis can be), then maybe something else with the Pi piggybacking the audio in?

I'm really looking forward to getting this stuff put together, and would love any thoughts or feedback.

That's going to be a pretty cool portable repeater once you get it done. You are on the right path, but I should add that you do have to lug around a lot of bulk and weight with what you list. If you use what you list then you should consider the Comet CA-712 as it weighs about 2# and no longer than a paint pole when broken down. The Ed Fong garbage is a waste of space and money, stick with a real antenna. As for the LMR-400, it's a compromise and more expensive than using Heliax reel ends, which can usually be had for free for lengths averaging +/-50'. As for the repeater controller, I use and recommend the much loved and bulletproof ID-O-Matic.

  https://hamgadgets.com/ID-O-Matic-IV-KIT_p_44.html

This setup will give you the best performance with very little added inconvenience. 

[WSAQ296]

Fun to build. But I happened upon a RT97L and other than the repeater ID it's all there. Built in,weatherproof. A pi-star with hamvoip or allstar on it can easily do repeater id, weather alerts, and custom announcements.  I could deploy this with a vehicle mounted antenna in minutes, and it'd run until the dc source stopped.  One connection (Okay two, power and antenna), easily programmed, and also capable as a local/base part of the equation. 
Antenna feedline loss is always the killer on low power repeaters.  Best to get the whole setup as high as possible, and then reduce feedline. 

The skywarn stuff, is available on a allstar node, you can build it all, lots of tutorials. Mine is not 'linkable'.  My raspberry pi-4, URI-x, and a serial cable make it easy.  There are other tricks for radios without pinouts for COS, ptt, etc.  Easiest is to use a sound card interface on the pi that actually is a uhf transmitter. 

[WRYZ926]

One thing I did not see mentioned is a duplexer. And yes you are going to want to use a duplexer since you plan on using a single antenna. 

[WRMR555]

1 hour ago, WRYZ926 said:

One thing I did not see mentioned is a duplexer. And yes you are going to want to use a duplexer since you plan on using a single antenna. 

It’s on the list! I picked up a used RFS 633-6A-2N for a pretty decent price.

[WRYZ926]

26 minutes ago, WRMR555 said:

It’s on the list! I picked up a used RFS 633-6A-2N for a pretty decent price.

That's what I get for trying to read and reply when I have too much blood in the caffeine system.

Dang dawg woke me up at 0530 this morning.

[WRMR555]

2 hours ago, WSAQ296 said:

Fun to build. But I happened upon a RT97L and other than the repeater ID it's all there. Built in,weatherproof. A pi-star with hamvoip or allstar on it can easily do repeater id, weather alerts, and custom announcements.  I could deploy this with a vehicle mounted antenna in minutes, and it'd run until the dc source stopped.  One connection (Okay two, power and antenna), easily programmed, and also capable as a local/base part of the equation. 
Antenna feedline loss is always the killer on low power repeaters.  Best to get the whole setup as high as possible, and then reduce feedline. 

The skywarn stuff, is available on a allstar node, you can build it all, lots of tutorials. Mine is not 'linkable'.  My raspberry pi-4, URI-x, and a serial cable make it easy.  There are other tricks for radios without pinouts for COS, ptt, etc.  Easiest is to use a sound card interface on the pi that actually is a uhf transmitter. 

The RT97L was my first consideration, but when I started digging into the DIY, I thought I'd be able to spend about as much or less to build my own with higher-output radios and additional controller features. I have everything I need to duplicate the functionality of the 97L except the repeater controller, and I'm only at about $460, so with a controller, that puts me at right about the market price on a new 97L. (I'm typing most of this to confirm it to myself more than anything...ha.)

I haven't dug into the pi-star/hamvoip/allstar stuff yet, but thanks for the new rabbit hole. Briefly, does the pi-star do the repeater controlling, or is it just feeding audio/etc. to a separate, stand-alone repeater controller?

[SteveShannon]

11 hours ago, WRMR555 said:

Initial questions

1. Any overall concerns about the current plan or components?
2. Coax: a lot of folks seem to push towards Heliax for repeaters, but I'm balancing loss against portability and cost. Thoughts on my -400 and -240 plan?
3. Repeater controller: recommendations? Again, I really like the ability for the repeater to say something like "Hurricane Watch. Flood Warning." when those things are active and I have internet access for the repeater controller, but I presume that would require using PI-REPEATER or something else that is inherently more complex than an analog, nonvolatile-memory-bearing controller. If the PI-REPEATER can be set-and-forget, great. If it's fickle (as Pis can be), then maybe something else with the Pi piggybacking the audio in?

I'm really looking forward to getting this stuff put together, and would love any thoughts or feedback.

Do it!

Yes, it would be easier to use the Retevis 97L, but it wouldn’t be nearly as fun!

As long as you keep your coax to a short length one of the ultra flex versions of 10 mm cable, like Messi & Paloni make will be just fine.  M&P shields are all copper for both foil and braid.  Times Microwave LMR 400 shielding uses two different metals for the foil and braid and people on RepeaterBuilder point to that causing problems only during full duplex operations, which is nearly all of what a repeater does.  I haven’t seen data to support those concerns. No matter what you do I would steer clear of cable with a solid center conductor like the plain old Times Microwave LMR400 uses. Get the best quality cable that works well for your use.
I agree with you about coax being better for portability than hardline. Do the math to see what your comparative losses will be, but if you truly want this to be portable you’ll want it to be easily coiled and laid out without fear of work hardening or eventual damage.

My experience with repeater controllers isn’t helpful in this case; the IDoMatic would probably be the easiest solution and then add something like a Pi to provide additional audio messages. In that way you’d still have the reliability of the ID-o-MATIC for repeater control if the Pi flaked out.

Keep us informed as you build it!

[WRMR555]

1 hour ago, SteveShannon said:

Do it!

Yes, it would be easier to use the Retevis 97L, but it wouldn’t be nearly as fun!

As long as you keep your coax to a short length one of the ultra flex versions of 10 mm cable, like Messi & Paloni make will be just fine.  M&P shields are all copper for both foil and braid.  Times Microwave LMR 400 shielding uses two different metals for the foil and braid and people on RepeaterBuilder point to that causing problems only during full duplex operations, which is nearly all of what a repeater does.  I haven’t seen data to support those concerns. No matter what you do I would steer clear of cable with a solid center conductor like the plain old Times Microwave LMR400 uses. Get the best quality cable that works well for your use.
I agree with you about coax being better for portability than hardline. Do the math to see what your comparative losses will be, but if you truly want this to be portable you’ll want it to be easily coiled and laid out without fear of work hardening or eventual damage.

My experience with repeater controllers isn’t helpful in this case; the IDoMatic would probably be the easiest solution and then add something like a Pi to provide additional audio messages. In that way you’d still have the reliability of the ID-o-MATIC for repeater control if the Pi flaked out.

Keep us informed as you build it!

Thanks for the tip on M&P. Their Ultraflex 10 looks promising: it's just below LMR-400-UF in cost per foot, has better attenuation in the 450 MHz realm (2.4 dB/100') than either LMR-400-UF (3.3) or LMR-400 (2.7), has a comparable bend radius, and weighs about the same as LMR-400-UF. It's towards the top of my list of options!

[WRUE951]

5 hours ago, WRYZ926 said:

One thing I did not see mentioned is a duplexer. And yes you are going to want to use a duplexer since you plan on using a single antenna. 

yup, important part hah.. mine is attached to one side of the can.  I would have preferred inside but it didn't fit.  

[SteveShannon]

42 minutes ago, WRMR555 said:

Thanks for the tip on M&P. Their Ultraflex 10 looks promising: it's just below LMR-400-UF in cost per foot, has better attenuation in the 450 MHz realm (2.4 dB/100') than either LMR-400-UF (3.3) or LMR-400 (2.7), has a comparable bend radius, and weighs about the same as LMR-400-UF. It's towards the top of my list of options!

They have two different flexible versions: Ultraflex and hyperflex. They also offer a cable called Airborne which uses aluminum in order to achieve a lighter weight. I have not evaluated it. There’s no reason to avoid aluminum as long as it’s prepared correctly when attaching the connector. M&P will also custom builb cables and ship them to you quickly. 

[PACNWComms]

Looks like a good build OP. Have used CDM-1250 mobiles for portable repeaters in the past, often in heavy Pelican cases with deep cycle marine batteries.....tripod mounted antenna up 30 feetor often got me 8-12 miles (placing it on the highest hill I could). 

Recently rebult this commercial unit that fell apart from many shipments across the country. Motorola CDM mobilebased as well.

 

[WSAQ296]

9 hours ago, WRMR555 said:

The RT97L was my first consideration, but when I started digging into the DIY, I thought I'd be able to spend about as much or less to build my own with higher-output radios and additional controller features. I have everything I need to duplicate the functionality of the 97L except the repeater controller, and I'm only at about $460, so with a controller, that puts me at right about the market price on a new 97L. (I'm typing most of this to confirm it to myself more than anything...ha.)

I haven't dug into the pi-star/hamvoip/allstar stuff yet, but thanks for the new rabbit hole. Briefly, does the pi-star do the repeater controlling, or is it just feeding audio/etc. to a separate, stand-alone repeater controller?

I got the 97L for a song, 280 bucks shipped. Open box, brand new. Everything was with it.  Ebay, at the right place/time.  Really a solid unit and I was showing 26 watts out into dummy load. 
The pistar/allstar setup can control or just announce. Can give you a courtesy tone, annoucnements, and skywarn plus.  I like tinkering with it.  Setup was rasperry pi - URIx radio interface- repeater.     The pi and URIx are always wired the same, but the pinout (db25) to repeater can differ.  The 97L was pretty easy.  Not sure you'll get COS, PTT and audio in/out from your mobile radio setup. Only because I'm not familiar with the radios you'll be using. 
 

[WRMR555]

11 hours ago, WSAQ296 said:

I got the 97L for a song, 280 bucks shipped. Open box, brand new. Everything was with it.  Ebay, at the right place/time.  Really a solid unit and I was showing 26 watts out into dummy load. 
The pistar/allstar setup can control or just announce. Can give you a courtesy tone, annoucnements, and skywarn plus.  I like tinkering with it.  Setup was rasperry pi - URIx radio interface- repeater.     The pi and URIx are always wired the same, but the pinout (db25) to repeater can differ.  The 97L was pretty easy.  Not sure you'll get COS, PTT and audio in/out from your mobile radio setup. Only because I'm not familiar with the radios you'll be using. 
 

Nice find on that 97L! That is a heck of a deal.
 

The TK-880s have OEM pigtails that you can attach to the control board and run out the power wire grommet to an  outside 9-pin connector. Alternatively, you can solder to a couple spots on the board to get COS, PTT, etc.

I intend to check the manual for pinout info and make a connector that will bridge between the pigtail and whatever controller or URI I use.

[WRYZ926]

I looked up the specs on the Kenwood TK-880 radios. My concern is that they have a low duty cycle of around 20% with the radio set to high power.  So they will get hot under heavy use while transmitting, especially on high power. Using low power will help.

The Retevis 97L is rated for 100% duty cycle. So it will handle heavy use better.

For comparison, part of the reason people have had over heating issues when using two Wouxun KG-1000G radios as a repeater is the lower duty cycle.

Just something to take into consideration. I do like to see what others come up with and build themselves.

[WRMR555]

9 hours ago, WRYZ926 said:

I looked up the specs on the Kenwood TK-880 radios. My concern is that they have a low duty cycle of around 20% with the radio set to high power.  So they will get hot under heavy use while transmitting, especially on high power. Using low power will help.

The Retevis 97L is rated for 100% duty cycle. So it will handle heavy use better.

For comparison, part of the reason people have had over heating issues when using two Wouxun KG-1000G radios as a repeater is the lower duty cycle.

Just something to take into consideration. I do like to see what others come up with and build themselves.

Thanks for the input. I've seen a few folks mention that the TK-X80H and TK-X90H radios work well as repeaters even at higher duty cycles if you bump them down about 20% from max power and put a fan on them. I figured 40W and a fan would be a good spot for me to start. Even at their most used, I don't see mine seeing significant use or long conversations. Either way, we'll see how it goes!

[tcp2525]

10 hours ago, WRYZ926 said:

I looked up the specs on the Kenwood TK-880 radios. My concern is that they have a low duty cycle of around 20% with the radio set to high power.  So they will get hot under heavy use while transmitting, especially on high power. Using low power will help.

The Retevis 97L is rated for 100% duty cycle. So it will handle heavy use better.

For comparison, part of the reason people have had over heating issues when using two Wouxun KG-1000G radios as a repeater is the lower duty cycle.

Just something to take into consideration. I do like to see what others come up with and build themselves.

Not an issue. If Yaesu can take two FTM-400s, a radio plagued with severe cooling issues and make a repeater out of them, he can get creative with cooling techniques and have a bullet proof system without worry.

[WRYZ926]

6 minutes ago, tcp2525 said:

Not an issue. If Yaesu can take two FTM-400s, a radio plagued with severe cooling issues and make a repeater out of them, he can get creative with cooling techniques and have a bullet proof system without worry.

I agree that there are plenty of ways to deal with heat. But I would be amiss if I didn't mention something about the low duty cycle.

[WRMR555]

Today's update: I decided on and purchased the Ed Fong GMRS antenna, for a few reasons made obvious by this handy chart:

Antenna	Gain (dBi)	Gain (dBd)	SWR	Height (in)	Weight (lbs)	Price
Ed Fong DBJ-UHF (GMRS)	5	2.85	<1.5:1	40	~1	$70.55
Comet CA-712EFC	9	6.85	<1.5:1	125	2.8125	$199.95

I want a good-enough antenna that will easily go atop a lightweight mast/pole, fit in the back of a truck when broken down, and be dummy-proof to set up. The Fong checked all those boxes, and came in at about 1/3 the price of the highly recommended CA-712EFC. I'd opt for the 712EFC if I was looking for something that was going to be even quasi-permanent, but that's not my goal. Besides, I can always buy a bigger base antenna for a base repeater later. (That's how this hobby works, right? )

Now, as for a portable mast, I'm looking for something that will get the antenna to the 20-25' range, collapse down to 5' or less, and be easy to carry and set up with one person (two if guy wires are necessary). Here are some options I've found thus far:

Mast	Maximum Height (ft)	Packed Height (ft)	Top Diameter (in)	Bottom Diameter (in)	Weight (lbs)	Material	Price
Jackite 28' Thick Tip Orange Fiberglass Windsock Pole	28	3.8	0.1875	1.875	5	Fiberglass	$89.95
SOTABeam 10m	32	1.92	0.15	1.929	2.9	Fiberglass	$80.44
MFJ-1915	25	4.79	1.02	2.165	6.8	Fiberglass	$159.95
MFJ-1913	28	3.83	0.333	1.83	4.4	Fiberglass	$129.95
Spiderbeam 10m HD	32.81	2.36	0.24	2.6	4.9	Fiberglass	$68.51
MFJ-1904HD	24	4	1	2.5	14	Fiberglass	$199.95
MFJ-1919EXAL	18	5	0.75	1.5	24	Aluminum/Fiberglass	$199.95
MFJ-1919EX	18	5	0.75	1.5	24.75	Fiberglass	$199.95

I've noticed that the lighter fiberglass telescoping masts have an incredibly small diameter at the top sections, which is great for wire antennas, but it clearly makes attaching a fiberglass or PVC antenna a bit more difficult. I'd seen a suggestion to keep the top few sections collapsed inside one another and then secure the antenna to those sections with clamps, or something similar.

Suggestions/recommendations, on either the mast or the securing method?

[marcspaz]

I built a portable repeater system for use in amateur radio, using a Yaesu repeater. I stuffed it in a Gator Case. It is 100% self_contained for use on UHF. You need to add an external duplexer for VHF. My biggest problem is that the repeater itself is so large that I couldn't find a waterproof case that was at a price point I could live with. 

 

I do like that setup in the tool boxes. I would slap a push/pull fan system on it for pull-through cooling and you could drop it anywhere, regardless of weather.  Right now, I deploy a 4-season shelter when I want to deploy it, or I run it out of the Jeep, if the weather is really bad and I don't need to be mobile while the repeater is in operation. 

 

I wouldn't worry about power so much, and focus on antenna hight. I have used a drone to drop ropes in trees and hoisted the vertical antenna well over 100 feet in the air. This gets you way better coverage than an antenna on a 20'-30' mast. This gets a little tricky if you are in a cityscape. But, buildings can be your friends. 

[WRYZ926]

56 minutes ago, WRMR555 said:

I've noticed that the lighter fiberglass telescoping masts have an incredibly small diameter at the top sections, which is great for wire antennas, but it clearly makes attaching a fiberglass or PVC antenna a bit more difficult. I'd seen a suggestion to keep the top few sections collapsed inside one another and then secure the antenna to those sections with clamps, or something similar.

Suggestions/recommendations, on either the mast or the securing method?

Most of those telescoping masts are probably going to be too small when fully extended. I do use one of those faraday cloth j poles with my 40 ft or 23 ft Spiderbeam masts, but that antenna is super light. The top of the masts still bend and blow around quite a bit even with the faraday cloth antenna and coax strapped down to the mast. The Ed Fong might be a little too much for the thinner masts as most are only 4mm to 6mm (5/32" to 1/4") diameter at the top.

I ended up going with the DX Engineering DXE-TFK25 telescoping mast so that I can use a 2m yagi or a 6m Moxon antenna. It is a bit on the heavy side compared to the thinner masts. The DXE-TFK25 collapses to right at 5 feet in length with all of the clamps installed. The DXE-TFK-25 is $238

I use mine with a hitch receiver flag pole mount. This is the mount I am using: EEZ RV Products Hitch Mount Starlink Pole and Flagpole Holder. It works well with both of my Spiderbeam and DXE masts without the need to guy them.

[tcp2525]

1 hour ago, marcspaz said:

I built a portable repeater system for use in amateur radio, using a Yaesu repeater. I stuffed it in a Gator Case. It is 100% self_contained for use on UHF. You need to add an external duplexer for VHF. My biggest problem is that the repeater itself is so large that I couldn't find a waterproof case that was at a price point I could live with. 

 

I do like that setup in the tool boxes. I would slap a push/pull fan system on it for pull-through cooling and you could drop it anywhere, regardless of weather.  Right now, I deploy a 4-season shelter when I want to deploy it, or I run it out of the Jeep, if the weather is really bad and I don't need to be mobile while the repeater is in operation. 

 

I wouldn't worry about power so much, and focus on antenna hight. I have used a drone to drop ropes in trees and hoisted the vertical antenna well over 100 feet in the air. This gets you way better coverage than an antenna on a 20'-30' mast. This gets a little tricky if you are in a cityscape. But, buildings can be your friends. 

Exactly! Getting a high gain antenna up high enough to clear obstacles will rule the day. He can run 5-watts to conserve battery and keep heat to a minimal. Design a portable system for efficiency and performance and everything else will fall in place.