866-867 MHz fringe coverage

Status
Not open for further replies.

IdleMonitor

Member
Premium Subscriber
Joined
Feb 17, 2005
Messages
2,766
Location
The Ottawa Valley - Eastern Ontario
So in the near future, I'm going to attempt once again to try and zero in on the 800 mhz to the east of me in the direction of Ottawa from Renfrew. (Mostly targeting the west end site for the Ottawa P25 system). Give or take I think the mileage should be about 60-80 km.

I found the proper duplexer and have a Comet CF-14B on order and shipped https://www.theantennafarm.com/catalog/comet-cf-413b-4355 This is used to separate my Discone antenna from the 3 element yagi with the yagi targeting the 800 mhz band.

I think the max I can get my 806-866 mhz PCTEL 3 element yagi MYA8063 https://www.tessco.com/product/806-866-mhz-6db-3-element-yagi-antenna-50858 is roughly 30 ft. maybe a bit less. If this yagi doesn't work out perhaps I need something just a bit bigger. I am prepared to buy another small yagi if I have to if this one isn't big enough to pull in the signal.

I'm also thinking about utilizing one of those low noise wideband amplifiers I see floating around on ebay to help with the signals. I don't have any issues with the discone and anything below 800 mhz. I have no 800 systems close to me other than Ottawa.

I'm guessing the typical LMR400/RG213 is too much for that band. What type of coax should I be going with? Also has to use N connectors.

If this doesn't get me what I'm wanting then I'll have to go with a bigger yagi or give up. I still think I should be able to get that system from my location.
 

VA3JPX

Member
Joined
Oct 3, 2005
Messages
75
Location
Ottawa, Ontario
For what this is worth, I use RG6 coax for my scanner setup. 1) It's cheaper 2) It's easily available at home depot. My antenna uses an F type connector that the coax can mate to. On the scanner side I use an F female to BNC male connection. As the scanner is not transmitting, the 75 ohm coax doesn't change the RX signal to the scanner by much. Way cheaper than LMR400.
 

mmckenna

I ♥ Ø
Joined
Jul 27, 2005
Messages
14,650
Location
SNCZCA01DS0
think the max I can get my 806-866 mhz PCTEL 3 element yagi MYA8063 https://www.tessco.com/product/806-866-mhz-6db-3-element-yagi-antenna-50858 is roughly 30 ft. maybe a bit less. If this yagi doesn't work out perhaps I need something just a bit bigger. I am prepared to buy another small yagi if I have to if this one isn't big enough to pull in the signal.
Depends a lot on the topography between you and Ottawa. 800MHz is really line of sight, so you'll need to have a really clean shot. Also, the radio systems you are trying to listen to are designed to keep coverage down in their intended coverage area as well as penetrate buildings. Not a lot of that transmitted power is going to make it out your way.

A 3 element Yagi isn't going to give you a lot of gain, and if you have a lot of obstructions between you and Ottawa, you're going to have some real challenges. If you get a bit of signal, using a higher gain Yagi may help improve coverage. But due to the line of sight challenges, you may need to get it up a bit higher.

I'm also thinking about utilizing one of those low noise wideband amplifiers I see floating around on ebay to help with the signals. I don't have any issues with the discone and anything below 800 mhz. I have no 800 systems close to me other than Ottawa.
But no doubt you have lots of cellular sites between you and Ottawa. Those high power cell sites running in the 700 and 800MHz bands can overload your receiver, so you need to be careful adding preamps. You may need some good filters to keep the cellular stuff from overloading your receiver.

I'm guessing the typical LMR400/RG213 is too much for that band. What type of coax should I be going with? Also has to use N connectors.
Depends entirely on the length of cable you need. More cable = more loss. I'd probably use LMR-400 for anything less than about 40 feet. Above that, you'll want something like LMR-600, 1/2" Heliax, etc. You'll probably have a very weak signal to work with (if any) and you'll need to do everything you can to get that weak signal to your radio.

If this doesn't get me what I'm wanting then I'll have to go with a bigger yagi or give up. I still think I should be able to get that system from my location.
There are some tricks you can play with Google Earth if you draw a line between your location and the closest tower. You can look at elevation profiles and that will tell you a lot. If there is a lot of dirt (hills) between you and them, you'd probably be better off saving your money.
 

IdleMonitor

Member
Premium Subscriber
Joined
Feb 17, 2005
Messages
2,766
Location
The Ottawa Valley - Eastern Ontario
Funny thing is. On some days. I can go 3 kms from my location and sit in the local Walmart parking lot and pick up this system. While mobile. Elevation change is minimal other then being mobile.

On the discone side. My current run of coax from the discone antenna to the home entry point I believe is LMR 400 at about 50 ft. About 25 ft inside is the same to an old cable splitter. One side going to the living room with a other few feet say 10 ft. of the LMR 400 to the radio with a short jumper.

From the splitter to the upper level of the home is old RG6 cable that was there from am old cable connection.

I have no problems with my signals from everywhere else on VHF low/air/VHF/UHF/UHF/MilAir etc.. I seriously pull in great signals from all around.

And when conditions allow I pick up some that I don't usually expect.

It's just a matter of pulling these 800 MHz signals out. Coax wise If I can get away with RG6 from the 800 antenna to the entry point with proper adaptors for the N connection then I would do that keeping costs low.

Once I get this. Then I have to try and figure out a way to zero on in the direction for the signal.

Interestingly enough kind of off topic. On the weekend I hooked up a simple antenna outside to use while on the back deck on top of the clothes line pole on my back deck. Maybe what 12 ft...?

Noticed a UHF frequency from Pembroke was coming in quite well. This frequency doesn't however come in for me on the base with the discone up almost 30 ft. Go figure.
 

mmckenna

I ♥ Ø
Joined
Jul 27, 2005
Messages
14,650
Location
SNCZCA01DS0
Funny thing is. On some days. I can go 3 kms from my location and sit in the local Walmart parking lot and pick up this system. While mobile. Elevation change is minimal other then being mobile.
Could be local noise, or could be some slight variations in topography.
I run an 800MHz system, and it really likes clear lines of sight. I can run south for about 60 miles and the system works great, but a dip in the road or run behind a hill, and it's totally gone. 800MHz works great for building penetration, but not so much for long haul stuff.

On the discone side. My current run of coax from the scanner to the home entry point I believe is lmr400 at about 50 ft. About 25 ft inside is the same to an old cable splitter. One side going to the living room with a other few feet say 10 ft. Of the lmr 400 to the radio with a short jumper.

From the splitter to the upper level of the home is old rg 6 cable that was there from am old cable connection.
Well, as you know, the average discone starts to suck as you go up in frequency. A dedicated 800MHz antenna will help.
Cleaning up with cable run and sticking with one type of cable will probably help you a bit. The splitter usually drops a bit over 3dB of signal at each port, 3dB is half your signal. If you can eliminate the splitter, you'll get some better performance.

I have no problems with my signals from everywhere else on vhf low/air/vhf/uhf/uhf/MilAir etc.. I seriously pull in great signals from all around.
Sounds like you have a good location. The lower frequencies would work better as cable losses are lower and the discone is going to perform better. I think adding a dedicated Yagi for 800 is going to help things.

What I'd do, if I was in your shoes, is take the yagi up to the roof with a short jumper and your scanner. See if you can get the system that way. If you can, then some additional gain and good cable will get that signal to your radio.
 

IdleMonitor

Member
Premium Subscriber
Joined
Feb 17, 2005
Messages
2,766
Location
The Ottawa Valley - Eastern Ontario
That would be probably be the ultimate starting point. I could mount the small yagi on the same pole right below the discone. That would get me my highest point. Then sit there with a short piece of coax and try and zero on the direction. That of course would be the absolute shortest run without any amplifier involved. If the signal is there, then I can easily work with the rest of it. It would of course mean I'd have to climb up there and do this. :p

Otherwise, my other thing is to use a pole (I'm not sure how long the one I can have access to use, but it's gotta be atleast 20 maybe 30 ft long) and attach it to the clothesline pole on the back deck and try for a signal there. That would be the easiest starting point without climbing up to the roof in order to search for the signal.

What I'd do, if I was in your shoes, is take the yagi up to the roof with a short jumper and your scanner. See if you can get the system that way. If you can, then some additional gain and good cable will get that signal to your radio.
 

mmckenna

I ♥ Ø
Joined
Jul 27, 2005
Messages
14,650
Location
SNCZCA01DS0
Otherwise, my other thing is to use a pole (I'm not sure how long the one I can have access to use, but it's gotta be atleast 20 maybe 30 ft long) and attach it to the clothesline pole on the back deck and try for a signal there. That would be the easiest starting point without climbing up to the roof in order to search for the signal.
The pool cleaning poles are a good option, if you can find/borrow one. Painting poles, etc, will work.

Yeah, stay off the roof if you don't need to be there. Those igloos you guys have up there can get slippery. You might fall off and land on one of your sled dogs;)
 

IdleMonitor

Member
Premium Subscriber
Joined
Feb 17, 2005
Messages
2,766
Location
The Ottawa Valley - Eastern Ontario
Judging by a quick look over Google Earth, as far as the land layout and topography is concerned. The land looks pretty flat to the direct east of me. I mean, we are in The Ottawa Valley and it's pretty much the valley part that I'm looking to get through.

The direction I'm looking to achieve looks like it's almost a NE direction, but not quite an East direction.
 

gary123

Member
Joined
Sep 11, 2002
Messages
1,340
Idle: Your on the right track. Using RG8 or good 50 ohm cable is the first step the lower the loss at 800 the better. All the amplification in the world wont work if there is nothing there to amplify. The eBay amps are okay but be careful many of them have no overload protection and a strong nearby signal can blow them. As far as topography is concerned, yes it plays a big factor.

The fact you can pick up the signals in Walmart parking ( don't tell them or they will try and bill you for it LOL) may be from the store acting like a huge reflector and concentrating the signal.

Here is how I would do your testing. First setup a SDR on a laptop and sit it on the CC your interested in. Connect a piece of coax from the yagi to the SDR. Then use the signal "spike" to look for a peak while you spin the yagi. Remember the spike level Once you know the best direction remount your yagi pointing in that direction reconnect the normal cable run. The slight height difference should not matter.

Next, connect the laptop to the cable run you normally use inside the house and compare the spikes. If there is a significant difference you may have to look into options like better low loss cable (at 800 MHz). I would 100% be using N connectors. The yagi should already have a N female. Without going into math and all kinds of other criteria. There is a reason Commercial installations are all N connectors. If PL259 was as good/efficient then they would be the standard.

OH and for those who think RG6 is fine. Your right, BUT with major reservations. First your going to be dealing with 2 75-50 ohm impedance mismatches.

RG6 is not rated for 800 or anything. It is used in satellite because the LNB outputs a ton of signal and is using 75 ohms. This is deliberate on the part of the LNB manufacturers. They are aware that many do "home" installs and use dollar store cable (100 feet for $8.99 I checked) and dollar store connectors ( dont ask... OK you asked 10 for $1.50). This is fine with signal levels through the roof. Most are living right under/near the sites so there is signal galore.

Basically you could use anything as cable in those circumstances. Also the lower the freq (no matter what cable is in use) the better the cable works. Again I'm not going to go into the math. And that's why it works on scanners.

Having said that if your using dollar store RG6 go ask your local cable guy or satellite installer for some of the professional grade stuff they use (dont forget connectors). Bring along a $10-$20 Tim's card (who does not like free coffee?). Maybe he will even put the connectors on for you. Just changing the cable will give you a 10% or more increase in signals to your reciever.
 

IdleMonitor

Member
Premium Subscriber
Joined
Feb 17, 2005
Messages
2,766
Location
The Ottawa Valley - Eastern Ontario
I finally got the diplexer in the mail this week and also got a 30 ft pole that I plan on using. So now, I would really like to know what I should go with as far as coax is concerned for the 3 element directional antenna?

I am really trying to save money because I will have to buy some other coax that I'll be using as well for another discone antenna that's gonna go on the same pole as well for my SDR at some point.
RG6, RG8, LMR400/RG213?

The directional antenna of course will be utilizing N connectors so the coax should match. I'm gonna need at least 60 ft for the run. The discone I'm not worried about. Just wanna try with this antenna though.
 

mmckenna

I ♥ Ø
Joined
Jul 27, 2005
Messages
14,650
Location
SNCZCA01DS0
Of the options you listed, LMR-400 would be the better choice of those.

1. You can install proper connectors on it easily. Yes, you can get UHF or N connectors that will fit on RG-6, but they are not common, you'll need to order them specifically, and you'll be making it harder than it needs to be.
2. Your system will be happier with 50Ω impedance throughout.
3. If you ever decide to get your amateur license, LMR-400 will be a better choice for transmitting.

You can do better than LMR-400, but you can also do a whole lot worse. It's a good mid-grade cable. It'll cost more than the other options, but good coax is always a wise investment.
 

gary123

Member
Joined
Sep 11, 2002
Messages
1,340
Anything along the lines of 1/2 heliax will serve you fine. There are a lot of suppliers to choose from so you should be able to get a good price. If you are particularly brave you could check out the local radio shop. It's not uncommon for them to sometimes have a short used spare roll laying around from a uninstall.
If the cable is clean (shiny) and NOT bent sharply or crushed. it may be something you can use.
 

prcguy

Member
Joined
Jun 30, 2006
Messages
10,513
Location
So Cal - Richardson, TX - Tewksbury, MA
I would start with a larger Yagi, you can get big ones with well over 10dBd gain for cheap these days. Then I would place this filter and amplifier right at the Yagi. You would be able to run any coax you please after that since the amplifier will boost the signals at the antenna and drive a long run of coax.

For a few more $$ you can add Bias Tees at both ends and feed the voltage up the coax, if the diplexer will pass DC. If not put the bias Tee before the diplexer and run DC wires over to the amp.

I would not use an amplifier without a filter in front of it.


 
Status
Not open for further replies.
Top