Updating Base Antenna 700/800 mhz

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teebee

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I am looking for a better performance 700/800 mhz outside antenna (25-30' High) for my BCD536HP scanner than I am currently using. I am currently using a Scantenna I purchased from RS several years ago (RG6 "F" connector w/75-300ohm converter). I also have a Discone antenna from Radio Shack using LMR-400 coax. I have also used another antenna from radio shack 20-176. Having said all this I do get best results from the Scantenna than the other two I mentioned with the Discone being the worst. What I don't like about the scantenna is even though its suppose to be a unidirectional ant., I still have to turn it when I want to pick up sites around me (30-40 miles away) in either direction. Never can I receive them simultaneously from all directions. Having said all this, I am looking for something that is Unidirectional (without having to turn it), that is just as strong or stronger than the scantenna with good gain. Of course I don't wont something super large. Scantenna is a little larger than I'd like.
I have been looking at the Panorama BS-800 762-894 5db gain. Anyone have any luck with this antenna and would it meet the qualifications I referenced to as for as unidirectional and reception gain or does anyone have a better recommendation. Its time to replace the old stuff any upgrade. BTW, I will be using LMR-400 coax (hopefully its still good) Thanks
 

marksmith

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You will probably have difficulty finding an omnidirectional antenna that performs as good as your directional one, in the directions which you turn it.

Going from directional to nondirectional is sort of like going from an antenna specific to one band to an all band antenna. You will probably get broader coverage across the board, but suboptimal performance in any one direction or band.

Mark
536/436/WS1095/HP1/HP2/996T/996XT/996P2/396XT/325P2/PSR800/15X/others
 

teebee

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Totally understand. I also have an 800 mhz yagi (not too good for 700mhz) that worked very well when everything was 800 mhz near by. But as for as the scantenna I thought it was suppose to be omnidirectional, unfortunately it will not do great unless I turn it to pick up certain sites. Just does not make since. Thats why I want one that has high gain and omni that will pick up equal in all directions
 

br0adband

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Looking at that Panorama BS-800 it definitely looks like a great antenna, but then I think about that price and realize - and this is my own opinion so take it as such - I'd never pay that kind of price for such an antenna knowing that I could build one myself (literally) in 20 minutes that would probably work just as well if not even better: a 1/4 wave ground plane, made from an SO-239 chassis mount that costs like $4 and some #12-14-16 gauge electrical wire or even some cut sections of coat hangers.

And I'm not kidding in the slightest.

The issue I think you're having it the distance you mentioned which is quite a chunk to be receiving 700/800 MHz communications since those frequencies don't really propagate all that well as such distances and you could also have obstructions in the signal path from the transmitter sites which are going to reduce the signal strength even more. From what I've gathered in research about the Scantenna over the decades - even in spite of it's popularity - is that it does have some weaknesses such as it not truly being a very omnidirectional antenna, especially in the higher frequencies you're hoping to monitor (because they are highly directional as it is).

The Panorama antenna is nothing special when you look at the design, and to be perfectly honest if you could locate an old cellular antenna (mag mount, clip on, whatever) you'd do pretty well in the 800 MHz range but not quite so well in the 700 MHz (since it would be cut for about 880 MHz).

The idea of making your own 1/4 wave ground plane gives you a) something to do, b) something to be proud of, c) something you can experiment with and build more because they are so cost effective and pretty fun to make, and d) cut it to precisely the frequency you want. In fact, you could make one cut to 772 MHz and also one cut to 855 MHz and use both with a coupler and probably do just fine. If you just make one antenna you'd want to cut it for about 820 MHz so it would be effective for both the 770 MHz and 850 MHz bands pretty equally.

But that distance is always going to be a major issue and if the transmitters sites and systems you wish to monitor really are 30+ miles away you have two options: get a signal amp + either buy or build a 1/4 wave ground plane antenna cut to 820 MHz to get as much of the signal to the scanner as you can or (maybe) get a signal amplifier + a Yagi antenna you can either buy or build (yes you can build those too) cut to the same 820 MHz center frequency and point it as required to really pull in the best signal you can.

A 1/2 wave ground plane might offer some better performance but I can't speak for the exact amount or offer specific figures in terms of decibels for signal strength, obviously. The distance from the transmitter site (the biggest concern), the antenna (next biggest), the height you place it at (a major factor), the coax you use as the feedline (pretty important to offset potential loss because of the signal propagation distance but LMR-400 should be excellent for that purpose as long as you're careful about the final length), it all works together to either provide you something the scanner can make use of or hearing more static than voice but I'm pretty sure you already know all this. ;)

I'd say build you own, in fact build a few different ones on the cheap, see what happens, if nothing you create is functional to improve things, then consider a commercial antenna (hopefully one that's not quite that expensive) and of course a high quality LNA someplace in the signal path could offer some improvement as well.
 

teebee

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I thought about cutting the discone and/or the Radio Shack 20-176 I currently have to the length needed for 700/800. First not sure if that would work any better and secondly I would not even know what the measurements would need to be to get that freq. range
 

br0adband

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1/4 wave ground planes are simple to make, and you can use any of a bunch of online calculators like this one to figure out the correct main element wavelength:

Amateur Quarter Wave Ground Plane Antenna Calculator

A 1/4 wave ground plane cut for 820 MHz would have a main vertical element of 3.424 inches - doesn't have to be absolutely perfect but close enough so 3.5 inches would work great without any issues to worry about. The ground plane elements could be 4 inches (slightly longer is my recommendation).

The issue with cutting the RS discone is once you do that kind of mod there's just no turning back and it's vastly easier to just construct your own antenna, it really is very simple to do with just that SO-239 chassis mount and some thick(er) gauge wire or coat hangers cut apart to the necessary element lengths.

Can't hurt to experiment, you might be pretty surprised at the results, and you'd obviously save a huge sum of money you can put towards other purposes like an LNA that could help with reception on top of having a properly tuned antenna to cover the range you need to monitor.
 

teebee

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Thanks for the guidance on the calculations. I've always thought about building my own. As for as no turning back on the discone, that would not matter because its garbage for my purpose anyway. I was probably going to dump it or sell it online. I'm sure someone could use
 

mmckenna

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Building your own antenna is a good option.

Another option is to purchase a used 800MHz high gain omni directional vertical. You can often find them use on e-bay and the like. It's pretty easy to get 9dB of gain out of a vertical on these higher bands without the antenna getting too big.

RG-6 is pretty good for this, however you may want to use some higher grade coax since feed line losses are significant at higher frequencies. LMR-600 would be a good start. 1/2" heliax would be a bit better. I've got a conventional 800MHz repeater here at work fed with about 40 feet of 7/8" heliax. My main trunked system is fed with 1 5/8" Heliax.
Reducing your feed line losses is important.

Other option is to install a pre-amp at the antenna. I've got a tower top RX preamp on my trunked system to help with performance.

An 800MHz vertical is going to work fine on 700MHz. If you can find a 700MHz vertical, that would work, too.
 

teebee

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Any suggestions on brands/models for some vertical 700/800 used antennas with that type of gain. Also I do have a stridesburg A8010 800mhz amp. It totally chokes out 700mhz.

I was kind of looking at the 824-896, 6dB, Laird Omni Base Antenna. I'm sure it may work some on 700 and better on 800mhz. Just not sure how well it will work on 700 as to thats the main area I need to target
 

mmckenna

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There's a lot of good options out there. For a base antenna at a home being used for receiving only, just about any will do. Avoid the "amateur" or Chinese brands.

If 700MHz is your primary interest, then get a dedicated 700MHz antenna, however you may not find as many of those on the used market.

---just checked e-bay, not much out there right now. Might have to expand your search if you wanted to go this path.

Making your own might be the better option at this point, though. Cheap, easy to do, and if it doesn't work, you are not out a lot of cash.
 

br0adband

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As I noted in another post just the other day which you can read here:

http://forums.radioreference.com/build-your-own-antenna/347412-custom-modified-700-mhz-scanner-antenna.html#post2709377

the chances of you finding a commercial 770 MHz dedicated antenna are practically zero because radio hardware that works in the 770 MHz must be designed to work with the 850 MHz range as well due to interoperability requirements meaning the comm systems have to be able to work across both bands. The need to have antennas and hardware that handles both bands means you'll find antennas cut to about 817-820 MHz so they cover both the 770 MHz and the 850 MHz range fairly equally.

The only real solution to a 772 MHz antenna requirement is literally to make one of your own. I've spent hours searching for a 772 MHz antenna (cut to that frequency specifically) and I've yet to find one over the past 2 year from any antenna maker. I'm sure you might be able to find some company that would make one specifically cut to that frequency for you if you requested it (some smaller antenna makers will take custom jobs) but that would be really costly.

Seriously, it's easier just to make one yourself as I mentioned earlier in this thread and you'll get good to great overall performance, especially if it's designed for that 772 MHz center frequency based on the 1/4 wave numbers I mentioned.

But look around, if you can find any commercial antenna that is cut for precisely 772 MHz or something close to it and not something in the 800 MHz range (to cover both bands) point me to it so I can look at the specs 'cause I've never ever been able to find such an antenna myself. The need for interoperability nowadays pretty much ensures that such systems will always end up with antennas cut to 817-820 MHz. Any antenna that claims 700 MHz operation - including the Motorola one I talk about and recommend in that other thread I just linked to - will be cut for the 817-820 MHz point to cover both bands, so be wary of any antenna that claims specifically 700 MHz tuning only.

As for an inline signal amp or LNA, there should be some designed to handle both bands as well - if it specifically says it's designed for 800 MHz then it's going to operate best there around 855 MHz and won't work that well for the 772 MHz area. It WILL work there unless it has some pretty awesome filtering going on and attenuation outside the operational design range but it should help to some degrees.
 
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teebee

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Thanks for all the response. I will give it a try to build one and see how it good it works. There are some mixed freq. on the Louisiana (LWIN) that uses 800mhz as well mostly 700mhz. So thats why I do need something that will cover 700 and 800.

I had this antenna listed in the link below I believe was used for a Siemens Phone system at one time. The antenna is by Engenius and I do think its a 900 mhz ant. with an N connector. I've tried it with LMR-400 coax in the past. I must say that did not work with the exception of a site real close to me. Would not perform more than that. I had wondered if there were any modifying it to work on the range I need. It suppose to have a 6db gain to it.
https://www.cdw.com/shop/products/Engenius-External-Antenna-20-meter/1015059.aspx?cm_cat=GoogleBase&cm_ite=1015059&cm_pla=NA-NA-ENG_WI&cm_ven=acquirgy&ef_id=WDznlwAAATmq8a-A:20170203205602:s&gclid=COPD1ZPo9NECFQqraQodktsO7g&s_kwcid=AL!4223!3!166686831481!!!s!56705819966!
 

br0adband

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Never ceases to amaze me how some antennas charge insanely high prices just because it's a commercial product. It's just a few pieces of metal and aluminum with some powder-coating most of the time and wow, the pricing is crazy but then again it's being resold by CDW and they are certainly not anyone I'd consider cheap on any product they carry.

Anyway, they are designed to cover frequencies based on this info I tracked down:

Engenius Durafon uses frequencies in the range of 902 to 928 MHZ.
so yeah, not a good antenna for dedicated 772 MHz operation and somewhat effective for 855 MHz functionality but obviously not something you can really make use of given your requirement for 772 MHz.

The gain rating doesn't really help much even in spite of it being that high because it's so far off the frequency band you're hoping to focus on.

Having said that if you still have that antenna you could - theoretically - just replace the vertical element with an element cut to 772 MHz and probably get good performance there as you're hoping for. The main vertical element on that antenna should just literally be screwed on and easy to remove, then replace it with one cut to 772 MHz but I'd still recommend cutting it to about 817 MHz so that it offers good performance in the 855 MHz band just the same. Experiment with different vertical elements and see how it goes. You might even be able to remove the vertical element from the original antenna in some manner and simply slot in a replacement element or even "a piece of wire" or coat hanger, you'll never know till you get to working with it.

Because that stock vertical element has the loading coil in it you can't just snip off some of the element itself and it'll automagically work, you'd need to work out the math to find out precisely how much to remove to retune it in the 772 MHz range (or again 817 MHz to be centered between the bands).

Since that antenna as it is won't help much I'd say get to modding it and maybe you'll end up with something that works great but it can't hurt to make your own 1/4 wave ground planes as well. At some point you'll mix and match stuff and end up with an antenna that does work better than what you've got presently.
 

marksmith

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Part of your issue may be the fact that newer p25 systems are configured such that the service area is the only place where they have coverage and those antennas that are 30+ miles away are specifically intended so that they don't go 40 miles in your direction.

Mark
536/436/WS1095/HP1/HP2/996T/996XT/996P2/396XT/325P2/PSR800/15X/others
 

teebee

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Picking up a SO-239 mount from RS now. Once I cut and put the rods on there how do you mount it to the pole.

Edit: Too bad they don't carry a N connector mount like this
 

lmrtek

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the panorama is just a mobile antenna on a ground plane

you can get a pctel BMAX7633s mobile antenna for $26.50 from solid signal

and the mbs800 ground plane for $28.99

you will have the same antenna for less than half the price
 

teebee

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Working on the custom build with the so-239 mount. I am still trying to figure the best way to mount this to a pole. Can you share a DIY solution.
 

br0adband

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A U-bolt or two? Some wire wraps? Self-locking cable ties? It doesn't have to be perfect, obviously, just something to keep the coax coming off the PL-259 connector along the pole (hoping it's not made of metal, PVC would be best if you have it), you'll figure it out.
 

trp2525

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Picking up a SO-239 mount from RS now. Once I cut and put the rods on there how do you mount it to the pole.

Edit: Too bad they don't carry a N connector mount like this
You CAN purchase an N connector chassis mount which would be better than an SO-239/PL-259 connector especially at 700-800 MHz. Here's one source that I found for $6.84 (from Triangle Cables of Missouri) but I'm sure there are other sources out there: N Female Solder Chasis Mount Connector For RG-58 | TriangleCables.com
 

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