Base Station Scanner Antenna Recommendations?

[rbritton1201]

I have a Uniden SDS200 Scanner connected to a Comet Discone Antenna, 25-1300 Mhz range, attic mounted. I realize it would work better if mounted on a mast outside, but that's not an option. The Discone is probably about 25' off the ground in the attic, and it receives VHF and UHF signals perfectly fine. The coax is RG8X in about a 100' length from the attic to the scanner. I plan to replace the coax with LMR400 to reduce losses that may be inherent in the RG8X.

I have a particular challenge receiving P25 signals via the Discone antenna off of one particular tower in my area, frequency range 773 Mhz. to 774 Mhz.. and the tower in question is located only about 6-10 miles away. But, the house is situated below the horizon, midway on a hill side, so geography may also contribute to blocking signals from this P25 tower. I receive signals from other P25 towers that are much further away, up to about 60 miles away, no problem.

I'm considering changing the antenna in the attic to the following:


DPD Productions Omni-X:

Or I'm also considering a Yagi that will provide some additional gain in one direction. I haven't researched a brand or model number for a good Yagi antenna for this purpose, one that would theoretically provide directional reception of this particular P25 tower. I would like to receive make and model recommendations from those that are having good performance with respect to P25 reception via a Yagi mounted in an attic.

The above DPD Productions "Omni-X" antenna comes very highly rated, and specifically when compared to a Discone antenna. DPD also manufactures vertical antennas that are specific to the 700 Mhz. frequency range that come highly rated for performance as well, but they're "omni-directional," but not wide banded. The Omni-X model above is omni-directional and wide banded, and I've read more positive reviews of the Omni-X antenna than the vertical antennas offered by DPD Productions.

I'm not sure, with the geographical issue of the antenna being below the horizon, if I would necessarily benefit from the directional characteristics of a Yagi versus the Omni-directional characteristics of the DPD Omni-X antenna above.

I'm open to testimonials relative to the DPD Productions Omni-X antenna above, as well as recommendations with respect to an attic mounted Yagi, if you believe a Yagi would benefit me more than the omni-directional "Omni-X" antenna, considering the geographical limitations of the antenna being situated slightly below the horizon.

 

[trentbob]

Before you go to all the trouble and expense, using low loss coax is a good idea and maybe you can do even better than lmr400 even though that's what I use and it is low loss. 100 ft is a pretty good run. Plenty of people here to give you more specific information but...

Before you spend the money... Try this... on the radio itself, using the menu button go to manage favorites> choose the favorites list that the system is on> review / edit systems> pick the system> edit site> choose the site you have the problem with> set filter... It should be on global which is normal by default, change the filter to wide normal then back out using the menu button and jot down on a piece of paper what filter you're listening to which is wide normal.

Listen for a while and see if reception improves from that site. If it doesn't then repeat all the steps above but this time pick invert, back out and listen, if no improvement then repeat the steps above and try wide invert. Back out and listen. You could find that there is no improvement on that site using one of those filters. If that's the case then repeat the steps above and put the filter back on global.

Avoid Auto filters as slow your scanning way down. If you find that wide normal, wide invert or invert helps with that site then just leave the filter on the site but hook up to Sentinel and transfer the data from your card to your profile so as to make the change permanent.

Maybe it will work maybe it won't but it's worth the try and doesn't cost a dime.

 

[murphcc1]

Just a side note on that........No need to keep pressing MENU to back out of the system.
Just press AVOID and it will bring you right out.

 

[trentbob]

I forgot all about that hahaha. Thanks. I have a list of other shortcuts and I never use them either LOL.

 

[sonm10]

This has been mentioned before in other threads - take the radio up into the attic and connect with a much shorter coax. If you have adequate signal, problem with the lossy coax. If you still don't have adequate signal, probably upgrade to yagi.

 

[vagrant]

100' is a long run for frequencies around 774 MHz. Can you reduce that to 75 or 50 feet? RG8X is definitely not a good choice due to the losses with that coax and frequency as you figured. Switching to LMR-400 would provide a noticeable difference for all frequencies. I would definitely switch to that first and then consider a different, or additional antenna later if you notice an improvement with that signal in question.

A discone is not the best choice for frequencies above 500 MHz unless they are nearby/strong. A discone in the attic will also suffer attenuation as well versus outdoors, but we must work within our limitations for whatever reasons. Still, if you are receiving transmitters 60 miles away that use 775 MHz, that is interesting. Topography and the transmitters height play a role for that distance.

A Yagi or omnidirectional antenna tuned for around 774 MHz will definitely help, but it will of course be a poor performer on other frequencies. A solution some use is two different scanners/receivers that handle different frequencies in order to ensure reception. Alternatively, you may find a diplexer that handles two different antennas to feed one scanner/receiver.

If the LMR-400 upgrade does not solve your issue, or at least improve it, I am skeptical if a tuned antenna may solve the problem due to your noted topography concern, even with the gain it would provide. If you do put up a directional antenna, you should test with it aimed directly at the transmitting station as well as a various degrees side-to-side due to the signal bouncing around at that higher frequency.

Update: Thinking further, do you have a cellular tower nearby, or in the direction of that particular tower? RF interference is something to consider.

 

[rbritton1201]

Well, I gave it a try, and unfortunately, none of the filter changes showed any bars of signal strength on the Washington 700 tower, nor was I able to hear any traffic. As you say, worth a try...but no cigar.

I'm considering whether to replace the RG8/X coax first, or install a new antenna to replace the Discone using the existing RG8-X coax, just to see if the antenna alone improves signal, or change out the coax first, then replace the coax if the antenna doesn't remedy the issue. If I can grab signal off this digital tower, which is totally dead right now, even two bars of signal strength, it would be adequate based on the performance I'm seeing from other towers, and I would be content.

I have a collection of various lengths of RG213 and RG8/U in my stash, a total of about 50 feet, which would reduce the amount of new coax I would have to purchase, which means I would have to purchase about another 50 feet of new Davis DRF-400, from Texas Towers. Since this run of scanner coax goes from my scanner to the attic, it'll save me quite a bit of money by using my stash to reduce the amount of new coax I have to purchase.

But, in order to join these lengths together, I would need about three or four barrel connectors, each of which are technically supposed to introduce some line loss. But, it's difficult to nail down just exactly how much line loss that would be. I've read anywhere from 10ths of a Db to as high a 2 Db. But, much of the commentary online relates to transmitting antenna systems, and not systems that are strictly dedicated to receive, such as is the case with a scanner. It seems from what I've read, that Db loss on "receive only" is much closer to 10ths of a Db of loss, which I can live with.

Of course, if Db losses are in the 2 Db per barrel connector range, then I would be foolish to utilize my stash of coax in the mix, and would be better off purchasing the full 100 foot length. since my labor to replace the coax is worth something too. I wish I could reduce the length of coax necessary, but that's the distance I have to work with in order to bring the coax from my radio room, which is in my basement, to the attic, where my antenna is located.

Try this... on the radio itself, using the menu button go to manage favorites> choose the favorites list that the system is on> review / edit systems> pick the system> edit site> choose the site you have the problem with> set filter... It should be on global which is normal by default, change the filter to wides normal then back out using the menu button and jot down on a piece of paper what filter you're listening to which is wide normal.

 

[rbritton1201]

There are cell towers between my base station location and the tower in question, there's about 6-10 miles distance between my base station where the scanner is located and the tower location. This particular police department is subscribed to both their local tower, as well as two towers that are much further away in opposite directions. The tower location is not a conventional radio tower, but on top of a water tower in this particular police department's venue. If you get just about a mile or two outside their city limits, it's common to lose the control channel signal off their localized tower, even if you're on a ridge, where you should be able to pick up the tower's control channel signal.

Many of us in the area speculate that this police department's local tower is on low power, as the signal strength seems to almost perfectly conform to the boundaries of this police department's city limits. Whereas, other towers in the MOSWIN system have signal ranges that are much greater. The way our system in Missouri is set up, there are two other towers within 15-40 miles of the city limits of this particular police department, and I can monitor signals off of either of these other towers. The towers are in opposite directions from the city limits of this particular police department, which leads me to conclude that interference from other cell towers is probably not the issue.

But, based on my prior experience, I don't think I'm hearing the full range of radio traffic I've experienced hearing in the past when this same police department was on an analog radio system. I would like to be able to pull in signals from the tower located within this particular police department's venue, so as to ensure that I'm hearing all the traffic on this particular police department's system. When I'm in their venue with my Uniden BCD436HP portable scanner, I can receive the tower that's within their venue, but reception is difficult once you get outside their city limits just a few miles.

I have my base station scanner set up to access the tower within their city limits, but the control channel is totally dead off this tower through my base station scanner, six miles down the road from this particular police department's local tower. I can access the towers that are further away, but because I believe I might be missing traffic that goes through these other towers that are further away, I would like to be able to receive signals off this particular police department's local tower via my base station scanner, so all I need is my cell phone to remotely monitor through my base station scanner, so I don't have to always drag my BCD436HP portable scanner with me all the time to monitor this particular police department's local tower. It's just a convenience issue, as I always have my cell phone with me, and I don't always have my BCD436HP portable scanner with me.

It isn't that I lose the full content of radio transmissions when they key up, each transmission between the base and cars seems to have continuity. But, it seems more as though I'm not hearing each round of transmissions, but that some transmissions are lost in the mix, like there may be some conflict between the police department's local tower, within their city limits, versus what signals I hear via other towers that are further away. So, I sometimes feel like I'm not hearing the whole enchilada, and that there is a division of transmissions taking place between this particular police department's local tower, and the ones that are further away, thereby omitting some transmissions.

Some of we locals speculate that this particular police department's local tower may be intended to assist with transmissions from portable radios that can't communicate with the towers that are further away, or to assist with reception in areas that are close to low lying areas on the other side of the Missouri river, where our Highway Patrol that's also on P25, has jurisdictional responsibilities, and that may be the case.

At any rate, my goal is to improve the coax and antenna system on my base station scanner to improve my system, even if I can't snag signals off this particular police department's local P25 tower.

Update: Thinking further, do you have a cellular tower nearby, or in the direction of that particular tower? RF interference is something to consider.

 

[trentbob]

There are cell towers between my base station location and the tower in question, there's about 6-10 miles distance between my base station where the scanner is located and the tower location. This particular police department is subscribed to both their local tower, as well as two towers that are much further away in opposite directions. The tower location is not a conventional radio tower, but on top of a water tower in this particular police department's venue. If you get just about a mile or two outside their city limits, it's common to lose the control channel signal off their localized tower, even if you're on a ridge, where you should be able to pick up the tower's control channel signal.

Many of us in the area speculate that this police department's local tower is on low power, as the signal strength seems to almost perfectly conform to the boundaries of this police department's city limits. Whereas, other towers in the MOSWIN system have signal ranges that are much greater. The way our system in Missouri is set up, there are two other towers within 15-40 miles of the city limits of this particular police department, and I can monitor signals off of either of these other towers. The towers are in opposite directions from the city limits of this particular police department, which leads me to conclude that interference from other cell towers is probably not the issue.

But, based on my prior experience, I don't think I'm hearing the full range of radio traffic I've experienced hearing in the past when this same police department was on an analog radio system. I would like to be able to pull in signals from the tower located within this particular police department's venue, so as to ensure that I'm hearing all the traffic on this particular police department's system. When I'm in their venue with my Uniden BCD436HP portable scanner, I can receive the tower that's within their venue, but reception is difficult once you get outside their city limits just a few miles.

I have my base station scanner set up to access the tower within their city limits, but the control channel is totally dead off this tower through my base station scanner, six miles down the road from this particular police department's local tower. I can access the towers that are further away, but because I believe I might be missing traffic that goes through these other towers that are further away, I would like to be able to receive signals off this particular police department's local tower via my base station scanner, so all I need is my cell phone to remotely monitor through my base station scanner, so I don't have to always drag my BCD436HP portable scanner with me all the time to monitor this particular police department's local tower. It's just a convenience issue, as I always have my cell phone with me, and I don't always have my BCD436HP portable scanner with me.

It isn't that I lose the full content of radio transmissions when they key up, each transmission between the base and cars seems to have continuity. But, it seems more as though I'm not hearing each round of transmissions, but that some transmissions are lost in the mix, like there may be some conflict between the police department's local tower, within their city limits, versus what signals I hear via other towers that are further away. So, I sometimes feel like I'm not hearing the whole enchilada, and that there is a division of transmissions taking place between this particular police department's local tower, and the ones that are further away, thereby omitting some transmissions.

Some of we locals speculate that this particular police department's local tower may be intended to assist with transmissions from portable radios that can't communicate with the towers that are further away, or to assist with reception in areas that are close to low lying areas on the other side of the Missouri river, where our Highway Patrol that's also on P25, has jurisdictional responsibilities, and that may be the case.

At any rate, my goal is to improve the coax and antenna system on my base station scanner to improve my system, even if I can't snag signals off this particular police department's local P25 tower.

Yep sorry that the filters did not work on that one site but yes it was worth a try. 1 filter I didn't suggest other than normal but you already have by default is... No filter at all. You could actually drill down the menu as before and take all filters off the site. I doubt it'll make a difference but...

As far as the mix and match of different coax using Barrel connectors to pair the 2 pl-259 connections oh, I don't know, if money is that much of an issue, I know it is for me, you are going to have loss.

There are experts monitoring this thread and they know better but I am familiar with installing antennas and was taught by my dad and uncle in the sixties as a teen, they were both ham operators and I picked up a lot of tips since then and have installed countless rooftop antennas since. At 100 ft run , you want the lowest loss coax you can afford, all in one piece if you can, I know you know that and we both know it's expensive.

 

[N0ZQR]

One thing that I keep having to tell myself is how far out of their intended coverage area and I

 

[KC3ECJ]

There's a 700/800mhz P-25 Phase II tower and some FMB wideband 900mhz broadcast links near me and I've had decent to great results depending on which site I'm monitoring. I'm using quad shield RG-6 and about a 55-60ft run. And a diplexer to separate VHF and below from UHF and above. Separate antennas. 40 some feet up in the air or so. Both are vertical dipoles. The UHF one tuned around 440/450, the VHF around 140/150.