remote radio repeater station

[Bala]

Where i work has a VHF repeater station, after being here 6 months as asked to look at it as someone stole a panel, looks like it draws about 8amps 12VDC when someone is talking, about 1amp? on standby

currently has one less panel as one was stolen, so only 2 panels that are putting in 12 amps when the sun is out.

Has 4 SLA 2 x old ones @ 100 amp hr and 2 x newer (2 years) @ 90ahr, 20a PWM controller, all 12V parrallel, radio runs direct 12V

You would have guessed by now that this is not all good, its wet tropics here so lots of cloud, it has rained almost daily for 6 months now, perhaps 2 weeks of sunny days.

looked through the history on the reg and 13V is about daily max and 12V min.

I have pulled one battery to charge and check but more to show the tech guy here that they are U/S, than I expect they will be any good.

How do you calculate load of a radio repeater like this where it depends on how much people talk, there would be a bout 40 radios that work through this with a LOT of daytime use and still quite busy at night at times.

[Mike90250]

How many years had it been running before someone stole a panel? If it was running well, I'd say someone guessed well at system configuration, and you just need to replace the missing panel. If it's started shutting off from low power, I'd say the batteries are shot and need to be replaced when you get the new panel. No sense adding new batteries now, undercharge will ruin them.

[Bala]

never thought of it like that, its been running for years and no one talks about it shutting down, it has had no failures in the 6 months i have been here and as i say its been raining a lot. were hoping to get the panel back, it is an island and people talk.

[Sunking]

8 amps @ 12 volts Xmt? That is some pretty low power. Assuming FM class C amp around 50 watts of Xmt power?

It is impossible for us to guess the Transmit duty cycle. Myself being a ham operator in Dallas TX area the repeaters get little use in a day with thousands of operators in the metroplex. However you cannot judge commercial to amateur operations because hams mostly use HF simplex SSB for DX. VHF and UHF FM is just too short of a range to be popular with hams.

So let's say 5% duty or 1.2 hours @ 100 watts, and 10 watts @ 22.8 hour give you roughly 350 watt hours per day. That is pretty easy to make.

But I am going to ignore all that for 1 reason, the batteries of AGM of 400 AH @ 12 volts is the key. For AGM you can as low as C/20 charge up to C/4. So a panel in that range is what we are looking for. C/20 seems to fit this application and if using a PWM charger and standard 12 volt panels on a 400 AH stack would be 20 amps x 17 volt = 340 watts ought to be plenty to satisfy the requirement.

[Bala]

thanks guys, it will take me a month or two to get new batteries, or a a realistic price any way, I will run the current batteries through on an ac charger one at a time, see if out other panels comes back and check the panel specs and see if i can get ones to fit in with what we have,

[axis11]

It seems your equipments are running well as it is. You can still make it more efficient and extend the life of the of the radios and batteries. I think you are throwing more power than what the users need. At 10amps of power draw,its about 50watts of transmit power just as sunking said. How far is the repeater from the weakest receiving station(portable,mobile)? Are you on high ground? If the users dont have problem triggering the repeater, its more likely that you can reduce to medium(25 watts) or low power(5 watts) transmit levels if the equipment has the capability.At low power setting, the cooling fan need not run anymore. It will be a lot of power reduction that will be useful especially during the cloudy days.

[Bala]

The repeater is on high ground ground but range needed in distance is 25km to the air strip, its also our best coms to our small boats traveling in open sea, as well as mobile and hand held units working in black spots behind hills around the drill sites. So will need to keep the power we have, its wet tropics and the system is stored in a plain tin shed so day time temps of 30c to 35c are the norm, obviously nice and warm in the tin shed where the system is, so the cooling fan will need to stay as well.

Appreciate the options though.

[Sunking]

The repeater is on high ground ground but range needed in distance is 25km to the air strip, its also our best coms to our small boats traveling in open sea, as well as mobile and hand held units working in black spots behind hills around the drill sites. So will need to keep the power we have, its wet tropics and the system is stored in a plain tin shed so day time temps of 30c to 35c are the norm, obviously nice and warm in the tin shed where the system is, so the cooling fan will need to stay as well.

Appreciate the options though.

So what is the Xmt power?

50 watts?

Are you using a high gain omni-directional antenna and low loss coax?

[Bala]

So what is the Xmt power?

50 watts?

Are you using a high gain omni-directional antenna and low loss coax?

I dont have the foggiest idea!!

Im a mechanic who knows a little about stand alone solar,

just put some new outboards on a boat and need to catch the tide to put it back in the water,

[Bala]

Well the boat is going ok,

the battery i removed from the bank and charged seems to be ok, after charging on a good multistage charger i put about 40w of load on it for an hour and it stayed up at 12.7 or so.

I was going to refit it and charge another this afternoon but it rained and I cant get the car up the hill when its wet.