Repeater & Antenna Problems. Advice needed!

[CommunicationsAlways]

I'm having problems connecting/talking to a repeater.

Info:
- VHF P25 Digital, Analog, Conventional, narrow band; Repeater, Base, Mobile, Portables.
- Repeater hight is 5,200+ feet (aprox.)
- Base/mobile height is 150 feet (aprox.)
- 300+ (aprox.) foot hill between repeater and base/moble.
- The only accesible repeater in my area.
- Line of sight is 30-35 mile to repeater.
- Cannot install a self suporting tower (Rohn, etc.) due to power line.
- Station transmits/receives VHF; Interopoability, U.S.C.G., S.A.R. Channels.

Any solutions or antennas?

Private messages, or post reply OK!

[Wowbagger]

How far is the hill from the repeater and/or the base?

[Jim202]

Why can't you install a tower due to a power line?

Where is the power line in relation to the house?

Have you looked at using a yagi antenna?

Jim

[CommunicationsAlways]

EDITED & MORE INFO
I'm having problems connecting/talking to a repeater.

Info:
- VHF P25 Digital, Analog, Conventional, narrow band; Repeater, Base, Mobile, Portables.
- Repeater hight is 5,200+ feet (aprox.)
- Base/mobile height is 150 feet (aprox.)
- 300+ (aprox.) foot hill between repeater and base/moble.
- The only accesible repeater in my area.
- Line of sight is 30-35 miles from BASE/mobile to repeater.
- Cannot install a self suporting tower (Rohn, etc.) due to Power Line, Phone/cable service line and two BIG trees!
- The only CLEAR AREA has a Gas service line.
- Station transmits/receives VHF; Interopoability, U.S.C.G., S.A.R. Channels.

Any solutions or antennas?

Private messages, or post reply OK!

[Bill_G]

Post the lat long of the repeater
plus band of operation (you said VHF - I'll assume 144-148)
plus the antenna elevation on the tower (otherwise I'll assume 50ft)
plus the antenna gain if known (otherwise I'll assume 3db dipole)
plus repeater xmit power (otherwise I'll assume 50W)
plus repeater rcvr sensitivity (otherwise I'll assume -116db)
plus any known losses - duplexer, line loss (otherwise I'll assume 4db total)
Plus the same info for the base/mobile (otherwise I'll assume the same info above, at 6ft elevation, 1db loss)

I'll post a worst case propagation plot here.

A picture tells a thousand stories.

[escomm]

Post the lat long of the repeater
plus band of operation (you said VHF - I'll assume 144-148)
plus the antenna elevation on the tower (otherwise I'll assume 50ft)
plus the antenna gain if known (otherwise I'll assume 3db dipole)
plus repeater xmit power (otherwise I'll assume 50W)
plus repeater rcvr sensitivity (otherwise I'll assume -116db)
plus any known losses - duplexer, line loss (otherwise I'll assume 4db total)
Plus the same info for the base/mobile (otherwise I'll assume the same info above, at 6ft elevation, 1db loss)

I'll post a worst case propagation plot here.

A picture tells a thousand stories.

this

[Bill_G]

The OP sent me his lat long in priv msg.

That is one tall mountain with a super clear view of the valley. You could swing a wire on a can over a tree branch and get good signal from that. This is the portable talk in with -106db at the rptr rcvr using the assumptions above. If you can't hit that, then start looking at everything - antenna, line, rcvr, site noise, etc. This repeater on Saddleback should be a boomer unless it is impaired somehow.

As always, red bad, green good, yellow that 12db place in between. Red is -116db (12db sinad point) and below. Yellow is -116 to -104db (poor to good, picket fencing, fade). Green starts at -104db and gets betterer.

Cheers!

[tvsjr]

What antenna is the OP using? Maybe something with a narrow vertical beamwidth that's "overshooting" his intended subscribers?

[CommunicationsAlways]

The OP sent me his lat long in priv msg.

That is one tall mountain with a super clear view of the valley. You could swing a wire on a can over a tree branch and get good signal from that. This is the portable talk in with -106db at the rptr rcvr using the assumptions above. If you can't hit that, then start looking at everything - antenna, line, rcvr, site noise, etc. This repeater on Saddleback should be a boomer unless it is impaired somehow.

As always, red bad, green good, yellow that 12db place in between. Red is -116db (12db sinad point) and below. Yellow is -116 to -104db (poor to good, picket fencing, fade). Green starts at -104db and gets betterer.

Cheers!

With a portable I don't have any trouble receiving repeater signals or the surrounding stations signals.

The closest station doesn't hear/copy when I transmit, I tried the portable at 5 watts with no success at a height of 10 feet above ground (Roof).
I'm getting very low repeater kickback at roof level when testing and moving to a different location doesn't help.

The only other option I have, is to try a directional antenna with a mobile.

Any suggestions on a quality directional antenna for a mobile?

Not worried about cost for the antenna!

[Bill_G]

With a portable I don't have any trouble receiving repeater signals or the surrounding stations signals.

The closest station doesn't hear/copy when I transmit, I tried the portable at 5 watts with no success at a height of 10 feet above ground (Roof).
I'm getting very low repeater kickback at roof level when testing and moving to a different location doesn't help.

The only other option I have, is to try a directional antenna with a mobile.

Any suggestions on a quality directional antenna for a mobile?

Not worried about cost for the antenna!

Wait! Not done yet. Might have to refine the map. So, you can hear the rptr with a portable on the ground, but you can't hit it until you gain some elevation. A site on a hill like that could be popular. Site noise could cause some degree of impairment that you couldn't do anything about. In high band, 10db desense is not unusual at a busy site. That's horrible, but not unexpected. 10db desense (or more) puts the rcvr threashold assumption at -106db which is the predicted talk in RSSI of a portable on the ground at the lat long you gave me for your house. Sounds like we're in the ballpark. Trying to overcome 10db of noise will take brute force like a high power xmitter, and it won't leave you much fade margin. A high gain antenna will help a little, but it could make things worse since you're trying to work a station beyond the horizon. The path calc says you would need almost 2 degrees of uptilt on a yagi. So, it must be visible to some degree from your location.

But, are you sure the rptr is where you think it is because that is the peak of range almost a mile up. Is it lower on the face someplace?

[Will]

Looks like Santiago Peak in Orange County. Which repeater is it, there are hundreds of radios on that hill?
They have a nick name for that site, Sh** Hill due to the noise floor and intermod.

And where are you located, there are some parts of the coverage area that are like sink holes to RF.

[Bill_G]

Looks like Santiago Peak in Orange County. Which repeater is it, there are hundreds of radios on that hill?
They have a nick name for that site, Sh** Hill due to the noise floor and intermod.

And where are you located, there are some parts of the coverage area that are like sink holes to RF.

I was afraid of that. So, 10db desense is probably not a bad assumption.

[escomm]

OP, where are you at? I can hit Santiago with a portable from the Valley... on a good day

[Bill_G]

OP, where are you at? I can hit Santiago with a portable from the Valley... on a good day

His base station is in the Downey area (according to the coordinates he gave me). I refined the plot based on how he says a portable works, Will confirming that there is a good chance the repeater receiver is impaired to some degree, and Google Earth confirming there are several sites on the peak. He said his portable doesn't work at ground level (6ft), but does almost work standing on the roof (15ft). I plugged in loss and increased the confidence until I could simulate that in the model. Looks like about 17db of receiver desense will cause these conditions 90% of the time. And here is the purdy pitcher from the purdy pitcher making machine ...

Red is -99db and lower. Yellow is -99 to -87db. And green is -87db or greater.

[Bill_G]

A couple things I liked about this problem - it illustrates the effect of receiver impairment on system performance, and it demonstrates hill shadowing.

You can do everything right, build the best repeater system in the world, and be crippled by a raised noise floor at your primary site. A high hill is not a good hill if your radio is deaf. You can overcome some of this by using a voting receiver system. Strategically placed receivers can recover inbound traffic so the talk in more closely matches the talk out. Plots like this, and user experience, help you determine where to place those receivers. It adds cost and complexity, but it solves a problem you have no control over.

I was also fascinated by the hill shadowing in this plot. Just north of the repeater (center of yellow circle) is a great example. I noticed it in the first plot, but the second plot really shows it well. At first I thought it might be lack of downtilt in the antenna pattern. We've all experienced that. Someone puts a monster gain antenna on top of a building or low hill. There's no coverage in town - the intended service area - but it covers two towns away just fine. Swap out the antenna with a simple unity gain loop, and the problem is solved. However, in this case, the hill itself is shadowing the surrounding area. An antenna at 50ft on a 5000ft mountain is proportionally insignificant. The immediate terrain still comes into play. Santiago Pk is the high point on a ridge, but just to the N and NE of the site, the ridge remains relatively constant (a haystack instead of a pointy peak) for about a quarter mile creating this big hole in the coverage that you can easily see in the plot. You'd have to raise the antenna about 500ft to overcome it ... if you could get permission. Customers in the Corona area would tell you they can see the hill but can't hit the repeater because of the shadowing, and there's nothing you could do about it without a voting receiver system.

Great example. Love it.

[escomm]

That whole string of sites along the ridge in that area are infested with RF. Santiago, Modjeska, Pleasants, Sierra, and so on. Here is a simple and probably unrealistic map of UHF coverage at Sierra.

[escomm]

And another from a site that's slightly higher than OP's at Santiago

[Bill_G]

Yeah, I imagine the whole LA market can be a nightmare for RF because of the pop base. Lots of users, lots of site owners, and not as much coordination and cooperation as we would probably like to see.

I like your plots. I quit doing multicolor temp plots because they confused the high level decision makers. They want the bottom line - pass/fail. Three color seems to be all they can digest. Green good, red bad, yellow so-so. After that, their eyes go blank.

[Will]

I'm having problems connecting/talking to a repeater.
Info:
- VHF P25 Digital, Analog, Conventional, narrow band; Repeater, Base, Mobile, Portables.
- Repeater hight is 5,200+ feet (aprox.)
- Base/mobile height is 150 feet (aprox.)
- 300+ (aprox.) foot hill between repeater and base/moble.
- The only accesible repeater in my area.
- Line of sight is 30-35 mile to repeater.
- Cannot install a self suporting tower (Rohn, etc.) due to power line.
- Station transmits/receives VHF; Interopoability, U.S.C.G., S.A.R. Channels.

Would that be one of the new CAP repeaters?

If not, which one. We do not have a whole lot of information from the OP on the actual repeater.



And remember that some parts of Southern Calif. are RF sinkholes.

[CommunicationsAlways]

A couple things I liked about this problem - it illustrates the effect of receiver impairment on system performance, and it demonstrates hill shadowing.

You can do everything right, build the best repeater system in the world, and be crippled by a raised noise floor at your primary site. A high hill is not a good hill if your radio is deaf. You can overcome some of this by using a voting receiver system. Strategically placed receivers can recover inbound traffic so the talk in more closely matches the talk out. Plots like this, and user experience, help you determine where to place those receivers. It adds cost and complexity, but it solves a problem you have no control over.

I was also fascinated by the hill shadowing in this plot. Just north of the repeater (center of yellow circle) is a great example. I noticed it in the first plot, but the second plot really shows it well. At first I thought it might be lack of downtilt in the antenna pattern. We've all experienced that. Someone puts a monster gain antenna on top of a building or low hill. There's no coverage in town - the intended service area - but it covers two towns away just fine. Swap out the antenna with a simple unity gain loop, and the problem is solved. However, in this case, the hill itself is shadowing the surrounding area. An antenna at 50ft on a 5000ft mountain is proportionally insignificant. The immediate terrain still comes into play. Santiago Pk is the high point on a ridge, but just to the N and NE of the site, the ridge remains relatively constant (a haystack instead of a pointy peak) for about a quarter mile creating this big hole in the coverage that you can easily see in the plot. You'd have to raise the antenna about 500ft to overcome it ... if you could get permission. Customers in the Corona area would tell you they can see the hill but can't hit the repeater because of the shadowing, and there's nothing you could do about it without a voting receiver system.

Great example. Love it.

Has anyone used/had feedback on a PCTEL Bluewave Marathon Series LPA136174-6NF 136-174MHz Log Periodic Array antenna?

[Bill_G]

Has anyone used/had feedback on a PCTEL Bluewave Marathon Series LPA136174-6NF 136-174MHz Log Periodic Array antenna?

You're going to try to work this repeater with a portable, aren't you? That antenna is only 6db of gain. Depending on antenna height, cable type, and cable length, you might be able to do it, but you won't have very much fade margin.

See these charts for cable loss per hundred feet by freq and type.

Let's say you put the antenna at 15 feet with 50ft of RG-58 - approx 3db of loss - if the repeater is as impaired as I think it is, threashold squelch is -99db. Your 6db ant at 15 feet with 3db cable loss will hit the receiver at a -90dbm leaving you 9db of fade margin. Not much, but usable. You'll come through with some hiss.

If you kept the antenna at 15ft, but used LMR400 instead, you'd recover 2db of loss which still brings you in with a little less noise.

If you used LMR400, raised the antenna to 30ft (adding 15 feet to the cable), you're now approaching -83db which should sound pretty quiet, and have enough margin to withstand some additional noise on the hill, or path fade which at 40 miles is going to happen.

Any high quality 6db antenna would do. It doesn't have to be a yagi. But, they won't be as nearly broad banded, and the price is about the same (if not much much more, a heck of a lot taller, and a lot heavier).

[Will]

Has anyone used/had feedback on a PCTEL Bluewave Marathon Series LPA136174-6NF 136-174MHz Log Periodic Array antenna?

Spending all that money for a PCTEL yagi antenna and you still do not know if anyone else can hit the repeater from your neighborhood. Some of us volunteered to check that for you.

[Bill_G]

Has anyone used/had feedback on a PCTEL Bluewave Marathon Series LPA136174-6NF 136-174MHz Log Periodic Array antenna?

Spending all that money for a PCTEL yagi antenna and you still do not know if anyone else can hit the repeater from your neighborhood. Some of us volunteered to check that for you.

That would be nice of you guys. Have someone with a mobile and a quarter wave see how well it works before he invests in an antenna and some kind of mast. It will at least be a sanity test of his portable, and the location.

We recently had a high band fire dept relocate to a cellular tower. 10db of constant, never ending broad band desense. And since they are not the incumbent, there is nothing they can do. Thankfully, we did not make the deal to move there. OTOH, I found a weather radar and microwave site on a mountaintop with a super quiet noise floor. I was hitting stations 100 miles away with a CDM mobile to a simple loop at 75ft through LMR. The HAAT is going to kill us on ERP. But, as a secondary site that fills from a different angle, it should be worth it.