PSR 600 Tweaks

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FireDawgEMT22

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I just got a PSR 600, and over all I am very impressed.

I do have some questions, I would like to monitor a P25 700mhz (771.50625 CC) system that is a single tower about 33 miles (line of sight) over flat terrain. I have this antenna Outdoor VHF-Hi/UHF Scanner Antenna - RadioShack.com about 35-45 feet up and a RG6 run of about 65 feet.

I cannot lock onto the CC. Is there a setting I am missing or can tweak to help this or is the transmitter just too low of a power to make it to me? According to the info on the RR database for this tower it says it has a range of 25 miles, but the 800 mhz system that this 700mhz system is piggybacked onto (same controller) can be heard over 40 miles south, but the RR database also says that system is only 25 mile range also.
 

gewecke

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I just got a PSR 600, and over all I am very impressed.

I do have some questions, I would like to monitor a P25 700mhz (771.50625 CC) system that is a single tower about 33 miles (line of sight) over flat terrain. I have this antenna Outdoor VHF-Hi/UHF Scanner Antenna - RadioShack.com about 35-45 feet up and a RG6 run of about 65 feet.

I cannot lock onto the CC. Is there a setting I am missing or can tweak to help this or is the transmitter just too low of a power to make it to me? According to the info on the RR database for this tower it says it has a range of 25 miles, but the 800 mhz system that this 700mhz system is piggybacked onto (same controller) can be heard over 40 miles south, but the RR database also says that system is only 25 mile range also.
I have the same radio (pro-197) and I'm thinking you might be lacking in the antenna dept. but let's go cheap first.
You said you are using rg6 right? How about maybe upgrading your coax to rg6 quad shield for less loss at 65' or even better some belden 9913 flex cable?
At trunking frequencies feedline loss is a big problem, so low loss cable is a must unless you're close to the system.

73,
n9zas
 

FireDawgEMT22

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I have the same radio (pro-197) and I'm thinking you might be lacking in the antenna dept. but let's go cheap first.
You said you are using rg6 right? How about maybe upgrading your coax to rg6 quad shield for less loss at 65' or even better some belden 9913 flex cable?
At trunking frequencies feedline loss is a big problem, so low loss cable is a must unless you're close to the system.

73,
n9zas
Thanks for the advice. Though I have a questions. From what I read and understand, and did some quick research again, RG6U (what I am using) and RG6UQ (quad shield) both have the same signal loss (5.56dB/100ft at 750MHz) So upgrading to the RG6UQ wouldnt yield much better results would it?

I have the antenna on my roof and run a splitter off of it with one lead going to an external antenna I added to my Minitor V charging base (yes I am a bit of a geek) and the other lead going to my scanner. Straight line from antenna to scanner is about 65-70 ft. Would I get noticably better results I just removed splitter, used that antenna only for my scanner and rerouted my cable to a run of about 45-50 feet, I would obviously remove the connector and cut down the cable to the necessary length also.
 

gewecke

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Thanks for the advice. Though I have a questions. From what I read and understand, and did some quick research again, RG6U (what I am using) and RG6UQ (quad shield) both have the same signal loss (5.56dB/100ft at 750MHz) So upgrading to the RG6UQ wouldnt yield much better results would it?

I have the antenna on my roof and run a splitter off of it with one lead going to an external antenna I added to my Minitor V charging base (yes I am a bit of a geek) and the other lead going to my scanner. Straight line from antenna to scanner is about 65-70 ft. Would I get noticably better results I just removed splitter, used that antenna only for my scanner and rerouted my cable to a run of about 45-50 feet, I would obviously remove the connector and cut down the cable to the necessary length also.
When you're wanting to receive comms that are not much less than microwave range, the better low loss cables available can make it seem like a new radio when used.
Here's a thought, belden 9913flex is rated at 1.4db loss per 100' @ 400mhz. (I goofed)
Sooo... imagine how minute your loss would be at 700/800mhz. with only 50' of cable? There are even other cables such as LMR400 and 600 with lower loss figures yet but then cost a bit more and serious overkill unless you also plan on transmitting. :)

After some further checking, I goofed on my figures so here is a table showing available cables and loss figures.

http://www.belden.com/techdatas/english/9913F7.pdf


73,
n9zas
 
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Swipesy

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I just got a PSR 600, and over all I am very impressed.

I do have some questions, I would like to monitor a P25 700mhz (771.50625 CC) system that is a single tower about 33 miles (line of sight) over flat terrain. I have this antenna Outdoor VHF-Hi/UHF Scanner Antenna - RadioShack.com about 35-45 feet up and a RG6 run of about 65 feet.

I cannot lock onto the CC. Is there a setting I am missing or can tweak to help this or is the transmitter just too low of a power to make it to me? According to the info on the RR database for this tower it says it has a range of 25 miles, but the 800 mhz system that this 700mhz system is piggybacked onto (same controller) can be heard over 40 miles south, but the RR database also says that system is only 25 mile range also.

You have spent $450 - $500 on a great radio and then you handicap the radio with a poor antenna system.

When you are on the very fringe of a radio system in the 700 - 800 range the signal is going to be weak so you need the best antenna system. So in your case I would do the following.

1. Buy a decent antenna. Multi-band antennas are not real good for 700-800 systems. Consider a Yagi pointed at the tower.

2. Buy decent coax like LMR400. Yes it is expensive but so is the radio.

3. Get rid of the splitter. It is eating up whatever little signal you are getting.

I have a similiar situation to yours and I use a Diamond J Discone with 50' of LMR400 for conventional frequencies running in to a duplexer and a Yagi 800 Mhz with 50' of LMR400 running into a Hamtronic amplifier and then into the duplexer and then the duplexer into the radio. Works beautifully. The amplifier on the end of the LMR picks up enough signal to give the signal enough boost to be able to hear a system that is 25 miles away.
 

FireDawgEMT22

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You have spent $450 - $500 on a great radio and then you handicap the radio with a poor antenna system.

When you are on the very fringe of a radio system in the 700 - 800 range the signal is going to be weak so you need the best antenna system. So in your case I would do the following.

1. Buy a decent antenna. Multi-band antennas are not real good for 700-800 systems. Consider a Yagi pointed at the tower.

2. Buy decent coax like LMR400. Yes it is expensive but so is the radio.

3. Get rid of the splitter. It is eating up whatever little signal you are getting.

I have a similiar situation to yours and I use a Diamond J Discone with 50' of LMR400 for conventional frequencies running in to a duplexer and a Yagi 800 Mhz with 50' of LMR400 running into a Hamtronic amplifier and then into the duplexer and then the duplexer into the radio. Works beautifully. The amplifier on the end of the LMR picks up enough signal to give the signal enough boost to be able to hear a system that is 25 miles away.

Trust me I know, the antenna is something I would like to replace, it is an antenna I purchased about 5 years ago when I went with external antenna, but I do not have the money for that right now honestly. I only got the scanner now because I couldnt pass up the deal at $300. Also I listen to all bands, and do not want to get into multiple antennas with one scanner. I have though about modifying the Discone and adding in either two 3.5" elements at the bottom of the verticles, or adding a single 3.5" element halfway up the VHF element.

Dealing with just the cable and doing some math, this is what I have came up with.

I have a 25ft section of RG8 coming off the antenna going to the splitter, and then about 60 feet of RG6 to my scanner.

Specifically looking at the 770MHz (what I want to monitor that is so far away) I am looking at about 1.4dB loss on the RG8 (5.7 dB at 100 feet RG8) and then the splitter is another 3dB loss (from what I have read passive 1 in 2 out splitter) and then about 2.78dB loss on the RG6 (5.56dB/100feet) total of 7.18 dB loss.

If I remove the 25ft RG8 going up to the antenna and remove the splitter and reroute the RG6 to about a 45-50 ft run I would reduce my dB loss to 2.78dB total.

I never really got into the dB loss figures before, and never worked in signal transmission like this where it mattered, I just assumed I was too far away. The more I have read and figured out how systems work I have figured out more about it all.

So with my system in place the way it is. If I am receiving 50% of the original signal from the broadcast tower, and 3dB loss is 50% reduction, I figure I am getting less than 10% of the original signal strength at my scanner.

By doing what I want with removing the splitter and rerouting, etc I should be able to get 2.5x's that and receive 25% of the original signal strength at my scanner.

I hope my math and research is correct. And if it is, adding the 800mhz element would further increase my signal reception. (Though to be honest I do not understand why, I always though a piece of metal will pick up any signal, the wave lengths and need for different lengths for each band is something I dont get. Time for more research.)
 
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rwier

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3. Get rid of the splitter. It is eating up whatever little signal you are getting.
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Not if it is the correct "POWER" splitter for his situation. It could make all the POSITIVE difference in the world. My view on this is not based on Forum "conventional wisdom", but on real life experiences that are REPEATABLE and PROVABLE.

Oh yeah, I completely agree with the rest, lol.
 

FireDawgEMT22

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Not if it is the correct "POWER" splitter for his situation. It could make all the POSITIVE difference in the world. My view on this is not based on Forum "conventional wisdom", but on real life experiences that are REPEATABLE and PROVABLE.

Oh yeah, I completely agree with the rest, lol.
It is just a passive 1 male and 2 female UHF splitter...and that antenna, I guess it would be more a ground plane than a discone..but still thinking about adding the 3.5" elements for 800mhz
 

tonycash

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It is just a passive 1 male and 2 female UHF splitter...and that antenna, I guess it would be more a ground plane than a discone..but still thinking about adding the 3.5" elements for 800MHz
Your on the right track, If you do the mods that you talked about and you are now just on the edge of
receiving the signals that you want, I'll bet you will receive it just fine with the mods to the coax. The loss
that you have now is really BIG so cutting that loss in half or more should help greatly.

73 de Tony, KD4K
 

FireDawgEMT22

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Well, I did the mods to the antenna, and removed the splitter. The wire run was actually worse than I thought, dont laugh, I didnt know much about cables and antenna when I put it up. It was running with a 25ft section of RG58 from the antenna to the splitter and then 60 feet of RG6 from the splitter to my scanner. So I figured I was getting about 11dB of loss from that.

I was not able to reroute the cable the way I wanted because the plan I had didnt pan out, but I did remove the splitter and the RG 58 cable, the 60ft of RG6 only reached fine. I figure that dropped my losses to about 5dB.

Over all, my reception is much better, especially on the VHF ( I cut the loss on VHF by a factor of 4 from about 8 to 2), I actually had to turn on the attenuator to get some of the VHF clearly.

Though I still cannot receive the CC on the 771.50625.

I started thinking about making my own 800mhz Yagi, since they seem simple enough and cheap enough. Though I do not want to lose my VHF reception. UHF would be nice to keep to, but not as much traffic that I listen to on UHF, mostly just VHF and 700-800 P25 systems with a single 800mhz EDACS in there (actually the completely opposite direction of the 700 I want to also monitor. Is there a such thing as a tri band Yagi or a Yagi with UHF and VHF whips?

Having lots of fun experimenting though...even have though about making a mast near my scanner location to further reduce the amount of cable, though that is a little pricey so it would have to wait.

Thanks for all the advice.
 
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