Antenna Suggestion

[scannerowner]

I'm researching what antenna would be best to use. I've got to put the antenna in the attic due to HOA rules, but it's a tall attic. I'm primarily monitoring VHF, but there are a few 700/800 sites I'd like to monitor around 15-30 miles from here.

I'm looking at either a discone or NMO ground plane kit with my all band Cometelco antenna on it. I just can't figure out which. I'm thinking about using 25ft of LMR-400 coax to use.

 

[flippinfleck]

No affiliation.

My DPD OmniX has worked well both inside and out.

OmniX Scanner Base Antenna

Specs Gain: 3 VHF 4 UHF dBi Pattern: Omni-directional Wavelength: 1/2 Elements: 3 Tuned: 118-137, 148-175 & 225-900 MHz Band: UHF & VHF Connector: N Female Cable: RG8X Cable Length: 16 Inches Height: 45" Width: 30" Weight: 2 lb Features Multi Band-Wide Coverage: The uniquely...

dpdproductions.com

 

[mmckenna]

I'm researching what antenna would be best to use. I've got to put the antenna in the attic due to HOA rules, but it's a tall attic. I'm primarily monitoring VHF, but there are a few 700/800 sites I'd like to monitor around 15-30 miles from here.

I'm looking at either a discone or NMO ground plane kit with my all band Cometelco antenna on it. I just can't figure out which. I'm thinking about using 25ft of LMR-400 coax to use.

Before you spend money on any antenna, make sure you know what your roof is made of. Any metal in the roof between your antenna and what you want to hear is going to impact performance. Also, any vapor barrier/foil backed insulation, lots of HVAC ducts, copper pipes, wiring, etc. can all be an issue. It would be a good first step to take your scanner up in the attic and make sure it works with the stock antenna.

Discone antennas are zero dB gain and have funky radiation patterns as they go higher in frequency. They can absolutely be a good option for some users. Their wide useable bandwidth can be a nice match to a scanner.
But, since you say that your primary interest is VHF and ~some~ 7/800MHz, you'll probably do better with something else.

The multiband Comtelco antenna would be my choice. Add the NMO ground plane, and you'll have an antenna that's designed for VHF, UHF and 7/800MHz bands. Since they are essentially 1/4 wave on VHF, it'll match the performance of the discone pretty close. On 7/800MHz, they actually have some gain, so will easily outperform the discone on those bands.
Since it sounds like you already own the Comtelco antenna, there's cost savings there, and that's always a good thing.

The NMO base station adapter will provide the necessary ground plane for the antenna to work as designed.
Mount the antenna up as high as you can in the attic to give it the best coverage. That'll also move it away from the noise sources inside your home.

LMR-400 would be fine, but make sure you can easily route it to the antenna. It's not very flexible and can be a challenge to route inside walls.
Also, you don't want to connect LMR-400 directly to the radio. That'll put a lot of strain on the antenna jack, and will risk damage. Use a short jumper for something like RG-58 for the final connection.
You could use something like LMR-240, which will have a bit more loss, however it's flexible enough to not strain the antenna jack on your radio. That means you can skip those extra connectors/adapters and probably recover some, if not all, that loss.

 

[Brales60]

No affiliation.

My DPD OmniX has worked well both inside and out.

OmniX Scanner Base Antenna

Specs Gain: 3 VHF 4 UHF dBi Pattern: Omni-directional Wavelength: 1/2 Elements: 3 Tuned: 118-137, 148-175 & 225-900 MHz Band: UHF & VHF Connector: N Female Cable: RG8X Cable Length: 16 Inches Height: 45" Width: 30" Weight: 2 lb Features Multi Band-Wide Coverage: The uniquely...

dpdproductions.com

That's what I'm using now, outside 20' up. I replaced a Sirrio Discone that worked good, but this one is better. Most of the stuff I listen to is in the 700's, but I have no issues with the airport and some rail stuff.

 

[scannerowner]

Before you spend money on any antenna, make sure you know what your roof is made of. Any metal in the roof between your antenna and what you want to hear is going to impact performance. Also, any vapor barrier/foil backed insulation, lots of HVAC ducts, copper pipes, wiring, etc. can all be an issue. It would be a good first step to take your scanner up in the attic and make sure it works with the stock antenna.

Discone antennas are zero dB gain and have funky radiation patterns as they go higher in frequency. They can absolutely be a good option for some users. Their wide useable bandwidth can be a nice match to a scanner.
But, since you say that your primary interest is VHF and ~some~ 7/800MHz, you'll probably do better with something else.

The multiband Comtelco antenna would be my choice. Add the NMO ground plane, and you'll have an antenna that's designed for VHF, UHF and 7/800MHz bands. Since they are essentially 1/4 wave on VHF, it'll match the performance of the discone pretty close. On 7/800MHz, they actually have some gain, so will easily outperform the discone on those bands.
Since it sounds like you already own the Comtelco antenna, there's cost savings there, and that's always a good thing.

The NMO base station adapter will provide the necessary ground plane for the antenna to work as designed.
Mount the antenna up as high as you can in the attic to give it the best coverage. That'll also move it away from the noise sources inside your home.

LMR-400 would be fine, but make sure you can easily route it to the antenna. It's not very flexible and can be a challenge to route inside walls.
Also, you don't want to connect LMR-400 directly to the radio. That'll put a lot of strain on the antenna jack, and will risk damage. Use a short jumper for something like RG-58 for the final connection.
You could use something like LMR-240, which will have a bit more loss, however it's flexible enough to not strain the antenna jack on your radio. That means you can skip those extra connectors/adapters and probably recover some, if not all, that loss.

I was wondering about that part of LMR-400. I attached a pic of the attic from our inspector before buying the house. Already a tv antenna as shown in there.

I think we should be ok, and I was thinking about using a splitter for 2 scanners, but the local stuff is all repeated, so almost scratching that idea to eliminate some loss.

Also adding a 2m/70cm antenna for HAM use.

 

[mmckenna]

I was wondering about that part of LMR-400. I attached a pic of the attic from our inspector before buying the house. Already a tv antenna as shown in there.

I think we should be ok, and I was thinking about using a splitter for 2 scanners, but the local stuff is all repeated, so almost scratching that idea to eliminate some loss.

Also adding a 2m/70cm antenna for HAM use.

Looks like it should be fine, especially if the TV Antenna works.

A splitter can be fine if you add some amplification to overcome the losses.

 

[scannerowner]

Looks like it should be fine, especially if the TV Antenna works.

A splitter can be fine if you add some amplification to overcome the losses.

Thank you sir! I think you've helped me make a decision. Both antennas would be as high up as possible, and separated as much as possible. Then coax dropped down to the shack.

 

[Ubbe]

Go up in the attic with a scanner and check what you can receive in the 700-900MHz range. A discone will perform worse than your scanners antenna in that frequency band. You can make use of that TV antenna, tilt it vertically and point it to those sites you wanted to monitor. Then check what you can hear from railroad and aircrafts as it seems to be a dual band VHF/UHF antenna. The RG6 coax it uses should be sufficient and at 25ft there's hardly any difference to a LMR400, that you instead can use for your transmitters.

/Ubbe