800 antenna to supplement a Discone

prcguy

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A lot of people are looking for the Holy Grail of antennas to cover everything but it hasn't been found yet. I am a big fan of the Discone for VHF/UHF over the VHF air band through 512MHz where the common size scanner types do very well. Above that range their pattern shifts upward and they loose a lot of gain at the horizon at 800MHz where I have personally measured about 10dB of drop.

For my personal setup I use a large Discone to cover the 118-512MHz range then supplement that with a tiny Discone that is rated for about 400MHz to several GHz then combine them with a diplexer. This gives me consistent gain across a very wide and picks up about 10dB in the 800MHz range over just the big Discone but overall I have no more gain than a Discone operated within its sweet spot.

I've been searching for a higher gain type antenna to cover the 700/800/900MHz range with some good gain but except for some high end commercial antennas with a big price tag, they are hard to find. At least until now. I found an antenna that will suffice for most people who need 800 band reception and this antenna is rated 6dBi gain or about 3.86dBd gain over the 824 to 960MHz range covering public service, trunking and 900MHz amateur. I probably works ok in the 700MHz range with reduced gain. Best part is they can be had fairly cheap on Ebay.

I just ordered one in the $34 range including shipping then found another seller at a cheaper price with many in stock but with a male N connector. No big deal, just install an N female on your cable or use a female to female adapter at the antenna and enjoy the $29 price tag including shipping.

Combine one of these antennas with a diplexer like the Comet CF-413 or one of the many commercial versions that will combine a Discone and this 800/900 antenna with the proper split. The end result will be the good and consistent performance of the Discone over the VHF/UHf range then about a 12-14dB boost over that Discone in the 800/900MHz range.

Here are a couple of ads for the cheap 800/900 antenna with free shipping.


 

MDScanFan

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Thanks for the heads up on this. It’s not my top priority right now been I have been planning to diplex a 800/900 antenna with my discone. I had been eyeing the Sirio HGO LTE which claims 5 dBi from 790-960. It was the best reasonably priced higher gain omni I could find that covered down into the high 700’s. I think the price is around $90. Please let us know how the L-com works out for you. The price is right.
 

vagrant

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I purchased an antenna very similar in specs back in 2015 via Amazon for $40. I use it with a 900 MHz radio 6' up inside the house. No problem hitting high elevation area repeaters with it 20+ miles away.

I use a quick release bar clamp as I rob it to use for RX with a scanner when I'm camping. I use a K&L diplexer (20-508 / 518-1300 MHz) with it for RX along with a discone. This post is quite opportune as I was recently looking to purchase another and it was no longer in stock. I have plenty of 1/2" Heliax and need to get the 900 up above the roofline at home, so dual duty will no longer work and need another.

Rats, no mounting plate, but at least it has N female. Hmm...well the "description" notes N female, but the picture is N male. I wonder if the seller knows the difference and why they have the wrong antenna pictured, or do they?

By the way, here is a sweep of the similar antenna I have mounted 6' up on a shelf. Every vertical segment is 42.857 MHz if you want to get an idea of what's what on the plot as it is from 700 to 1000 MHz.

789VSWR.jpg 789S11.jpg 789R.jpg
 

shirsch101

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Does the diplexor separate any overlapping frequencies between the 2 antennas? Say if the discone is a wide band and you add the 800mhz antenna does the diplexer block the 800mhz signals from the discone?
 

bobruzzo

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Cranston, Rhode Island
A lot of people are looking for the Holy Grail of antennas to cover everything but it hasn't been found yet. I am a big fan of the Discone for VHF/UHF over the VHF air band through 512MHz where the common size scanner types do very well. Above that range their pattern shifts upward and they loose a lot of gain at the horizon at 800MHz where I have personally measured about 10dB of drop.

For my personal setup I use a large Discone to cover the 118-512MHz range then supplement that with a tiny Discone that is rated for about 400MHz to several GHz then combine them with a diplexer. This gives me consistent gain across a very wide and picks up about 10dB in the 800MHz range over just the big Discone but overall I have no more gain than a Discone operated within its sweet spot.

I've been searching for a higher gain type antenna to cover the 700/800/900MHz range with some good gain but except for some high end commercial antennas with a big price tag, they are hard to find. At least until now. I found an antenna that will suffice for most people who need 800 band reception and this antenna is rated 6dBi gain or about 3.86dBd gain over the 824 to 960MHz range covering public service, trunking and 900MHz amateur. I probably works ok in the 700MHz range with reduced gain. Best part is they can be had fairly cheap on Ebay.

I just ordered one in the $34 range including shipping then found another seller at a cheaper price with many in stock but with a male N connector. No big deal, just install an N female on your cable or use a female to female adapter at the antenna and enjoy the $29 price tag including shipping.

Combine one of these antennas with a diplexer like the Comet CF-413 or one of the many commercial versions that will combine a Discone and this 800/900 antenna with the proper split. The end result will be the good and consistent performance of the Discone over the VHF/UHf range then about a 12-14dB boost over that Discone in the 800/900MHz range.

Here are a couple of ads for the cheap 800/900 antenna with free shipping.


Looks good. What type of mounting bracket can you use for this? Looks like a small antenna with small area to put a mount. Maybe radiator hose clamp?
 

MDScanFan

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Yes, that is the goal of the diplexer. Let’s say a discone is connected to the 1-500 MHz port 1 of a diplexer and a collinear 800/900 to the 800-1000 MHz port 2. Port 1 will be highly attenuated for >800 MHz such that any received signals on the discone will be highly attenuated (ex 50 dB). Port 2 will be passed along with minimal insertion loss at those frequencies.

Does the diplexor separate any overlapping frequencies between the 2 antennas? Say if the discone is a wide band and you add the 800mhz antenna does the diplexer block the 800mhz signals from the discone?
 

Ubbe

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If you accept a hole in the frequency between 550-700MHz you can use cheaper filters from mini-circuits, one low pass upp to 650Mhz and one high pass from 600-5000MHz connected to a T-adapter and coax to each antenna and one common coax to your receivers.

/Ubbe
 

MDScanFan

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The mounting bracket is shown in the L-com Link. The website indicates the antenna is sold as a kit with the bracket, but the eBay listings I have seen specifically state it is not included or do not show it. A separate eBay listing can be found for the bracket.
Looks good. What type of mounting bracket can you use for this? Looks like a small antenna with small area to put a mount. Maybe radiator hose clamp?
 
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MDScanFan

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You will not be able to diplex without a gap somewhere. The comet 413b referenced above is a good low cost, off the shelf option. You mainly lose the 500-750 region. Please see the thread here where I was looking for a diplexer recommendation.


Which diplexor would give me the best coverage of all frequencies without any gaps?
 

prcguy

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There is nothing to listen to on a scanner in the US between 512 and 698MHz except for digital TV so its best to find a diplexer with similar specs. Plus the antenna I recommended would not provide continuous coverage, its only intended for the 800/900 bands and it may be useful in the 700 range if you have that in your area.

There are some off the shelf diplexers that are perfect but very expensive like this one https://www.tessco.com/product/diplexer-public-safety-cell-80-520-694-270050w-120-325925 I've camped out on Ebay and have been able to pick up several commercial/military diplexers perfect for the job including the one above for very fair prices but they don't come up every day.

On the antenna mounting bracket, the antenna has a long N connector and is intended for the N connector to go through a hole in the mounting bracket or in the top of an outdoor box (that can house a filter and preamp!) then a nut will tighten the antenna to the bracket or box or whatever. You could probably mount the antenna at the top of a mast and use a hose clamp or two around the metal base.

Which diplexor would give me the best coverage of all frequencies without any gaps?
 

prcguy

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My goal is to use antennas that work well over all the frequencies you would need to monitor. For most people this would be 118-512MHz then about 850 to 870MHz for public service repeater outputs. If 700 is used in your area then your antenna might need to cover down to about 769MHz. There is some LMR in the 930MHz range so to me an ideal antenna to supplement a low frequency Discone would cover about 769 to about 940MHz with as much gain as possible.

The L-Com antenna on Ebay is about the closest thing I have found that is affordable for most people. The Comet 900 antenna mentioned above barely covers the 902 to 928 amateur band and is not good for 700 or 800 stuff. I have two of them and they barely work on a 902/927 split for my amateur repeaters.

I like the Comet KP20.

to
 

JoshuaHufford

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The L-Com antenna on Ebay is about the closest thing I have found that is affordable for most people. The Comet 900 antenna mentioned above barely covers the 902 to 928 amateur band and is not good for 700 or 800 stuff. I have two of them and they barely work on a 902/927 split for my amateur repeaters.
Would you say the L-Com works better than the KP-20? I have a KP-20 and use it to receive from 896-953 and it does well for me.

Do you have a different hobby grade antenna for the above range you would recommend?
 

mancow

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I have one surplused from a trunking system that looks like a sidewinder missile. I should sweep it and see what it covers but it seems to work well!
 

prcguy

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I just threw an antenna analyzer on a KP-20 with a 6" long jumper to see how its tuned. Each division on the analyzer is 28.57MHz so one division above 915MHz or about 943.5Mhz the antenna has about a 7:1 match and it gets to 9:1 just above that where performance will have dropped off drastically. In the lower 800 range its almost an 8:1 mismatch. The 2:1 points on the antenna barely make its rated 28MHz of BW.

So far the L-Com antenna is about the broadest band 800 antenna I have seen for a cheap price and I don't know of anything better unless you dive into a new commercial antenna at about $1k and up.

1.JPG






Would you say the L-Com works better than the KP-20? I have a KP-20 and use it to receive from 896-953 and it does well for me.

Do you have a different hobby grade antenna for the above range you would recommend?
 

vagrant

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I ordered one as well, but mine is not due until 9/24. I'll also sweep it as I am curious how close it is to my other one...and how different it may be from another others will receive.
 

Kaleier1

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i paid $15 for a 9 element 13 dbi yagi that works great but of course it is not omnidirectional.
 
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