Two Discone Antenna's (at same time)

[Saint]

Stick with the discone if your required bandwidth is that wide. Realistically there is no one antenna or even two together that will perform well over that range. What are you monitoring above 800-900 MHz? RG-8 will not perform well, there's too much loss at those frequencies.

I just do searches in the 900 to 1300 MHz band, GENERAL MOTORS USA, SAIA COMMUNICATIONS in Buffalo NY trunked systems are up there and also ham bands but I really do not listen to them that much, but I do searches in these bands for new stuff.
Steve

 

[prcguy]

A typical scanner Discone works well from about VHF air through 500MHz but not so good at 800MHz and above. You can put up an antenna like this for the 800MHz and up range then diplex the two antennas onto one feedline. TerraWave 800-2500MHz 3dBi Omnidirectional Antenna M4030030O10006T - 800088423 | eBay

 

[Saint]

A typical scanner Discone works well from about VHF air through 500MHz but not so good at 800MHz and above. You can put up an antenna like this for the 800MHz and up range then diplex the two antennas onto one feedline. TerraWave 800-2500MHz 3dBi Omnidirectional Antenna M4030030O10006T - 800088423 | eBay

OK nice antenna, I am also going to buy 50ft of RG8X coax for my scanning, it's better then what I have now.
Steve

 

[prcguy]

RG-8X is not good for much and I would not use that for a 50ft run on a scanner antenna. If you want to have any 800-1200MHz still left at the end of your coax go to something much bigger like LMR-400.

OK nice antenna, I am also going to buy 50ft of RG8X coax for my scanning, it's better then what I have now.
Steve

 

[Saint]

RG-8X is not good for much and I would not use that for a 50ft run on a scanner antenna. If you want to have any 800-1200MHz still left at the end of your coax go to something much bigger like LMR-400.

Would that be good for across all the bands, I know it's pretty stiff but the run will not be bent. I am looking for a coax that's good for all the bands from 108 to 1300 MHz, I know i'm asking a lot from coax but what would be a good choice.
Steve

 

[wtp]

try RG6.
loss is not bad and low cost.
yes, this is the coax for cable.

 

[prcguy]

For 50ft and up to 1200MHz I would use LMR-400 at the smallest. You will still have about 2.6dB loss at 1200MHz which is approaching loosing half your signal level. The same setup in RG-8X would loose about 8dB or about 80% of you signal at 1200Mhz and maybe more.

Would that be good for across all the bands, I know it's pretty stiff but the run will not be bent. I am looking for a coax that's good for all the bands from 108 to 1300 MHz, I know i'm asking a lot from coax but what would be a good choice.
Steve

 

[Saint]

Thanks everyone for all the information, I was either thinking 50ft run of rg6, rg8x or the LMR-400. I guess i'm going to have to make a choice.
Steve

 

[GTR8000]

Forget about tying the two antennas together. As others have correctly pointed out, the loss from the splitter and additional coax required would negate any benefits, which there wouldn't be with two discones anyway. Two Yagis with a phasing harness is a different story, but two discones is pointless. Waste of effort and money.

RG6 is okay for short runs, but if you're going to use 75 ohm coax, try to find some RG11 which is thicker and has loss specs more inline with LMR-400, and is usually quite a bit cheaper than LMR-400.

RG8 would be a good choice, with LMR-400 the best choice, as the loss is relatively low even at 1 GHz. Because it's 50 ohm cable, you don't have to mess around with too many adapters. 75 ohm coax like RG6 or RG11 will require F type connectors on the coax itself, then adapters to convert to BNC or SMA, depending on what you're connecting it to.

tl;dr - Connect to just one antenna at a time, and go for LMR-400 if you want the best performance

 

[prcguy]

There is only a fraction of dB loss in combining a low and high frequency antenna together with a diplexer, maybe .25dB and not an issue. You can use RG-6 or RG-11 or whatever, but in the end when you upgrade again to LMR-400 you will wonder why you didn't just do that the first time around.

Forget about tying the two antennas together. As others have correctly pointed out, the loss from the splitter and additional coax required would negate any benefits, which there wouldn't be with two discones anyway. Two Yagis with a phasing harness is a different story, but two discones is pointless. Waste of effort and money.

RG6 is okay for short runs, but if you're going to use 75 ohm coax, try to find some RG11 which is thicker and has loss specs more inline with LMR-400, and is usually quite a bit cheaper than LMR-400.

RG8 would be a good choice, with LMR-400 the best choice, as the loss is relatively low even at 1 GHz. Because it's 50 ohm cable, you don't have to mess around with too many adapters. 75 ohm coax like RG6 or RG11 will require F type connectors on the coax itself, then adapters to convert to BNC or SMA, depending on what you're connecting it to.

tl;dr - Connect to just one antenna at a time, and go for LMR-400 if you want the best performance

 

[GTR8000]

There is only a fraction of dB loss in combining a low and high frequency antenna together with a diplexer, maybe .25dB and not an issue.

The loss is greater than just "a fraction". You're not taking into account the loss from the coax going from the diplexer to each antenna, as well as the insertion loss of the additional connectors. You can't just count the loss from the diplexer itself.

Also, the OP mentioned wanting to connect what is essentially two identical antennas using a splitter, not using a proper diplexer for two antennas covering different bands. Apples and oranges.

 

[dlwtrunked]

Unless you place one directly above another, you are just as likely to get worse reception as better reception. In any case, the improvement is marginal--a few dB. I once had a commercially made discone of that sort (may still have it somewhere in my shed).

I meant to say "double discone of that sort". It was Italian made.

 

[dlwtrunked]

I might get better results upgrading my coax cable.
Steve

Agree, though higher is always better.

 

[Saint]

Agree, though higher is always better.

Just ordered LMR 400 COAXIAL cable 25' I'll give this a try and see if there is any difference, I have been procrastinating about changing my coax for a long time, now I will look for something better then the Discone antenna I have for 108 to 1300 MHz there should be something else out there that is comparably to the Discone antenna.
Steve

 

[prcguy]

Two short, probably less than 6ft LMR-400 jumpers, no loss to speak of and a pair of connectors on the jumpers, maybe .1dB loss total. Diplexer insertion loss maybe .25dB as I mentioned before. I don't know what you are worrying about, I do this all the time and it works great. The OP originally mentioned combining two identical Discones but a few posts later I offered the suggestion of two different frequency range Discones.

The loss is greater than just "a fraction". You're not taking into account the loss from the coax going from the diplexer to each antenna, as well as the insertion loss of the additional connectors. You can't just count the loss from the diplexer itself.

Also, the OP mentioned wanting to connect what is essentially two identical antennas using a splitter, not using a proper diplexer for two antennas covering different bands. Apples and oranges.

 

[dlwtrunked]

Just ordered LMR 400 COAXIAL cable 25' I'll give this a try and see if there is any difference, I have been procrastinating about changing my coax for a long time, now I will look for something better then the Discone antenna I have for 108 to 1300 MHz there should be something else out there that is comparably to the Discone antenna.
Steve

"Better" require further specification. If you want broadband, omni-directional, and in one antenna, there is likely noting better. If you drop braodband, omni-directional or one antenna, then the answer changes.

 

[JoshuaHufford]

Just ordered LMR 400 COAXIAL cable 25' I'll give this a try and see if there is any difference, I have been procrastinating about changing my coax for a long time, now I will look for something better then the Discone antenna I have for 108 to 1300 MHz there should be something else out there that is comparably to the Discone antenna.
Steve

Is 25' enough? I thought you said you had a 50ft. run? Good choice on the LMR-400, that in itself should help some.

If there is a single antenna that can do that wide of a range well I'd sure like to know about it. I will second the suggestion of keeping your current discone, get a diplexer and an antenna like prcguy suggested that can do the higher frequencies well.

 

[Saint]

Is 25' enough? I thought you said you had a 50ft. run? Good choice on the LMR-400, that in itself should help some.

If there is a single antenna that can do that wide of a range well I'd sure like to know about it. I will second the suggestion of keeping your current discone, get a diplexer and an antenna like prcguy suggested that can do the higher frequencies well.

After looking at the price I thought about it and can get away with 25 feet of the LMR 400. I wanted 50 feet just in case I moved the scanner in the apartment.
Steve

 

[AB5ID]

Try it and see what happens. You probably won't have a omnidirectional pattern anymore. Connecting 2 antennas will give you changes in phase that may hurt or help what your trying to listen to. Putting 2 50 ohm antennas in parallel will give you a vswr mismatch without the correct cable harness, not to mention splitter and connector losses already mentioned.

 

[Saint]

Try it and see what happens. You probably won't have a omnidirectional pattern anymore. Connecting 2 antennas will give you changes in phase that may hurt or help what your trying to listen to. Putting 2 50 ohm antennas in parallel will give you a vswr mismatch without the correct cable harness, not to mention splitter and connector losses already mentioned.

I will try it after I get my LMR-400 COAX I just received a email from Amazon that my lmr-400 has just shipped about an hour ago so when I see what difference the coaxial does Then I will order a splitter and try out the two Discones at the same time. Should be interesting.
Steve