Portable Repeaters

[BlueDevil]

Do you have a portable repeater? What is it? How is it powered? What bands does it operate on? Does it have linking capabilities? Is it a commercially/professionally built device or something you put together on your own?

If you were to built a portable repeater to deployed on large emergency incidents what would it be and how would you build it?

 

[nd5y]

Download the 2016 NIRSC User's Guide at National Interagency Fire Center
It has a lot of information on portable repeaters and links among other things.

 

[BlueDevil]

I am at NIFC right now taking the COMT class. I am familiar with their system but am curious what else is out there? What are people using when they don't have access to the NIFC radio cache?

 

[radioman2001]

I have owned and still do many MX portable repeaters one on 146 for CAP(not used anymore) one on 406 for operations North of Line A in NYS, one on 450 and another on 470 for NYC area. They originally came with crystals, and I updated them to the "S" platform radio insides. I am contemplating upgrading them to Astro portables if I find some at Dayton this year for a good price so that would give me P-25 capability.

I have also built for my agency one made from an Icom FR-5000 chassis in a Pelican case and using a mobile duplexer. Operates at 5 watt out on LI-FE battery, or 20 watts on external power. mainly used at scene of derailments and drills. It has the capability of accessing our wide area IDAS system to bring it down to the operations center at GCT, but has never been used that way yet.

While on the subject I have also built a few Command Radios using CDM-1250 and APX mobiles in Pelican cases for areas where a portable won't do the job. The CDM's are VHF and the APX is a VHF/450. Unfortunately the pictures I have are over 4 meg and won't load.

 

[902]

You can take two of just about anything and build a portable repeater, but it's tricky.

I've used PDR3500 repeaters (NIFC probably has one or two of those). I've made repeaters out of M1225 and GM300 radios. I've made repeaters out of Hamtronics boards. And, I also helped a manufacturer shield two Standard (brand) portables in a paramedic related product that's already been supplanted by other technologies.

Here are some things to consider:

1) Isolation. Usually this is a trade-off between cost, size, electrical characteristics, and frequency separation. AND, this can also mean installing the transmitter and receiver in shielded enclosures and using bypass capacitors and ferrite beads to minimize the effects of RF. Some commercially available products are deficient in that respect.

2) A "clean" transmitter. One that isn't "noisy" and emitting low level noise that will end up on your receiver frequency regardless of what you do. If you are unfortunate in this respect, you will need significant notch of your receiver frequency on the transmitter side of your duplexer. This might cause excessive insertion loss.

3) A "narrow" receiver. The problem with LMR equipment today is that they are made to operate over a wide range of frequencies. That's great if you've got a system that transmits on 170.15 and receives on 150.775. That's also a problem if you're attempting to simultaneously receive within that passband. You'll need to make up for that with an external preselector or pass/notch devices.

The PDR is external 12 V or 120 V. It's essentially a 25 Watt Quantar in a suitcase with a mobile duplexer on top. The paramedic radio I worked on was powered by a sealed lead acid battery. Hand-held radios could be NiCd, Lithium ion, NiMh, or AA batteries in holders. Maybe there could be a solar charger for rechargeable batteries. For my repeaters, I use Delco S-2000 deep cycle batteries. They're heavy as heck, but a known quantity.

I suppose the bottom line is your imagination and how you apply it.

 

[BlueDevil]

My next portable repeater project.

 

[NDRADIONUT]

A yaesu ft 8800 and ft-60 portables work well vhf out uhf in or the opposite.... The Ft 60 memories will store the 2 bands in memory either way....

 

[rfradioconsult]

Motorola PDR-3500, well constructed, operates on both 12V and AC. Software programmable, duplexer is mounted on top of package so it can be retuned or replaced in the field. We use them for airborne or placed on rooftops, etc. I used one to support our FEMA mission during the 2013 Moore, Ok tornado response. Does analog, P25, AES encryption.

 

[freddaniel]

902 did a great job outlining some basic considerations. Others are: maximum size allowed [bigger than a breadbox?]; power consumption [number of hours on battery without charge]; Frequency band, either VHF or UHF affects size of duplexer; cost limitations; designed for solar charge?; completely weatherproof; etc.

 

[PACNWDude]

Many of mine are on YouTube, using two Motorola CDM-1250's, or other mobile radios.

Go to repeaterbuilder and find all you need. Some have been with interface boxes from MRE1032 from eBay. Others have Motorola interface boxes and duplexers.

There are so many possibilities you could write and read books on the subject.

 

[jim202]

There is a major difference between good or well working and cheaply constructed portable repeaters.

Many people try to build a portable repeater out of 2 portable radios. This is not a very good choice because most portable radios have very poor shielding or receiver adjacent channel rejection. As a result, you get problems with the receiver when the transmitter keys up.

Then there is the issue of a good duplexor. You need some where on the order of 70 to over 100 db of isolation, depending on what transmitter power you try to run.

Using a good quality of double shielded coax cable for all connections between the radios and the duplexor. Don't try using cheap coax going to the antenna either. I don't recommend using any LMR type coax. You don't want to have to fight noisy problems out in the field in the middle of a hurricane or a major rain storm. The LMR cables have a history of causing noise in a duplex system due to the difference between the shield materials. There are those that say if you properly seal the connections, you don't have this problem. Well in a portable use application, your options are very limited on just what conditions you will set up the repeater in. So why even put yourself in the position of any possibility of any coax problems.

If you have to hike in the repeater, your going to want to limit the size of any battery system you plan to use. Maybe consider the use of a solar charging system to keep the battery system charged. I prefer to limit the installation to locations that I can drive to. This may take an ATV to get there, but I am not walking in any radio package.

No mention of an antenna system has been talked about. Depending on the frequency band, will determine just how large your antenna will be. I will not recommend the use of a 1/4 wave whip antenna. If your going to take the effort of putting a portable repeater into service, something better than a unity gain antenna really needs to be used. Your going to use more than a 1/4 wave whip on your portable radios, don't you think the repeater should at least use the same gain?

There will be those that will poo poo my comments. But I have been working with public safety radio systems for many years. One thing that has been drummed into me over those many years is do it right the first time. You may not be able to have a second chance to do it over to fix some oops that you took a short cut on. It's too late when you find your portable package doesn't work or doesn't work very well.

 

[kayn1n32008]

A yaesu ft 8800 and ft-60 portables work well vhf out uhf in or the opposite.... The Ft 60 memories will store the 2 bands in memory either way....

This is in the commercial/professional section, not the hammy toy section...

That said, the FT-8800 cross and repeat function is inferior to The TM-V71a. About all the yaesu is good for is to bring simplex, low powered portables back into a repeater on the opposite band. Downs side to it is there is a 500ms tail that can not be removed, the Kenwood does not suffer from that problem.

Moving on to the topic at hand,

I built 2 VHF portable repeaters back about 15 years ago that were made from a pair of Icom mobiles, 15A power supply, mobile duplexer, and a Zetron tone panel. They were built to pass 13 VHf repeater pairs that transmitted @ 153.xxxx and received 5.26MHz higher. Even had a 1/2wave antenna included in the kit. They could be runoff AC and 12v, they put out 5 watts at the output of the duplexer. Worked pretty good too.

 

[Project25_MASTR]

Built plenty off of 16 pin Motorola's. Favorite one was a SM50 based radio that we kept in the truck for ski season that ran at 10W. I haven't checked the XPR mobiles yet, but the 25-10W Motorola mobiles have the most thermally efficient PAs on them.

Tecnet has a nice little setup for building a repeater out of two mobiles but I haven't played with them much.

Hytera makes a nice little DMR/analog backpack repeater (battery, IP likable, internal duplexer).

I think Etherstack debuted a new P25 interop repeater at IWCE…very nice but very expensive.

If I were building analog only, I'd start out with a Hamtronics receiver (100 dB adjacent channel rejection is why) and use a heavily sunk data radio for transmit (cut out the circuitry you don't need) unless it needs to be manned by someone.

For P25, Simoco actually has a very nice configuration for turning two mobiles into a repeater. Received data is sent to the transmitter via serial communications. Best part is the price isn't too terrible.


Sent from my iPhone using Tapatalk

 

[902]

If I were building analog only, I'd start out with a Hamtronics receiver (100 dB adjacent channel rejection is why)

Oh, definitely!

I've built a bunch of Jerry's stuff over the decades. I've been a big fan of just about everything except his 6 meter transmitter board, which distorted when CTCSS was injected (which, I seem to remember making a varactor modulator to inject CTCSS about 20 years ago, but I'm not sure where that ever ended up... more than likely in my garage attached to the 440 repeater I used to use before I got the MSF).

Built quite a few of the boards into RF-tight boxes with feed-through capacitors as repeater blocks, RF links, Micor replacement boards for SpectraTac buckets, and the list goes on.

Last board I bought was an R313 which had outstanding sensitivity. I have another for a RX-only APRS IGATE.

I never discussed it with him, but it seems to me he's scaling back on his product line quite a bit. I don't see any of the 6 meter or 900 MHz strips at all anymore. Can't get any of the crystal ovens, either. I used 918 MHz links to backhaul a number of things a while back.

 

[Project25_MASTR]

Oh, definitely!



I've built a bunch of Jerry's stuff over the decades. I've been a big fan of just about everything except his 6 meter transmitter board, which distorted when CTCSS was injected (which, I seem to remember making a varactor modulator to inject CTCSS about 20 years ago, but I'm not sure where that ever ended up... more than likely in my garage attached to the 440 repeater I used to use before I got the MSF).



Built quite a few of the boards into RF-tight boxes with feed-through capacitors as repeater blocks, RF links, Micor replacement boards for SpectraTac buckets, and the list goes on.



Last board I bought was an R313 which had outstanding sensitivity. I have another for a RX-only APRS IGATE.



I never discussed it with him, but it seems to me he's scaling back on his product line quite a bit. I don't see any of the 6 meter or 900 MHz strips at all anymore. Can't get any of the crystal ovens, either. I used 918 MHz links to backhaul a number of things a while back.

Last I talked to him, V/U are all he is doing (synthesized now) at the time. He also is no longer getting his exciters typed for part 90.