Diamond 220R Discone For SDS200 (in attic)

[TailGator911]

My son will soon be the proud new owner of a Uniden SDS200 scanner. He lives in a strict HOA subdivision in La Jolla, and his only option for decent antenna placement is going to be in the attic. I am thinking the Diamond 220R mini-discone. I've never had to do an attic antenna, so this goes out to the antenna wizards here on the forum. I picked the 220R because I liked it so much on my RV, superb reception, and small enough for a confined space. He will be listening to San Diego county north, La Jolla, San Marcos, Escondido, Oceanside, etc. Public safety (I know a lot of E going around out there), he is a student pilot right now so I know he will be monitoring the county airports, etc. I will make a beginning profile for him on Sentinel and program some fav lists for him, then he can take it from there. So, for limited space in an attic, is a Diamond 220R mini-discone sufficient? What is considered the best indoor attic antenna? Thanks, guys!

 

[vagrant]

Much depends on what will fit and bigger is typically better for antennas. Some options are:
1. The Diamond 220R you noted
2. Tram 1410 discone which does not have the upper element and make it easier to fit and assemble in the attic.
3. A larger Diamond discone that can simply be put together without the upper vertical element, but a nut will be needed to hold things in place.

Still, if the attic has foil backed insulation on the roof he will have trouble with receiving. At that point something outdoors, even a few feet off of the ground would probably have better success. Also, if the 800 MHz stuff is not encrypted, a second vertical omni antenna tuned for 800 and a diplexer would probably improve receive of that higher frequency range. There is a thread on here by prcguy about the "L-com" antenna for that upper range.

As to coax LMR-400 is recommended, especially for the higher frequency stuff. An alternate is LMR-240UF (Ultra Flex) which is thinner and uses a stranded core to provide flexibility.

 

[chill30240]

I put a Tram 1410 discone in my attic 2 weeks ago and have been very pleased with the results. I had no other choice but to go that route even though I don't have an HOA to deal with. I don't have access to a ladder anymore since I retired so for what I use it for it works great. My SDS100 works like a champ.

 

[dlwtrunked]

My son will soon be the proud new owner of a Uniden SDS200 scanner. He lives in a strict HOA subdivision in La Jolla, and his only option for decent antenna placement is going to be in the attic. I am thinking the Diamond 220R mini-discone. I've never had to do an attic antenna, so this goes out to the antenna wizards here on the forum. I picked the 220R because I liked it so much on my RV, superb reception, and small enough for a confined space. He will be listening to San Diego county north, La Jolla, San Marcos, Escondido, Oceanside, etc. Public safety (I know a lot of E going around out there), he is a student pilot right now so I know he will be monitoring the county airports, etc. I will make a beginning profile for him on Sentinel and program some fav lists for him, then he can take it from there. So, for limited space in an attic, is a Diamond 220R mini-discone sufficient? What is considered the best indoor attic antenna? Thanks, guys!

Since no one else mentioned it, airport ground side is not much power and rarely on an antenna of sufficient height (it does not need to be as aircraft are high and in the clear). The ground side often cannot be heard more than 10 miels away and sometimes not that far. Just about any antenna will hear the aircraft. The ground side, no antenna might help--particularly one at a low height.

 

[TailGator911]

All good comments, thanks...there is no option for outside mast, antenna, or any hardware. This has to be in the attic. It's a roomy attic with a plyboard walkway and about 6'7" tall. No foil on insulation (that I know of) no metal shingles. Mexican tile roof. The rest of the house is blown insulation. Antenna will be right over radio room, just pop a hole in the ceiling of the closet and drop the LMR down and scanner is on table right there, maybe 10-12 ft run. I can't travel out there right now due to health issues, but a good ham friend has offered his services so I know he is in good hands. Just have to make a decision on the antenna. Leaning more to the 220R only because I had such good results with it mounted on the roof of my Winnebago Via with a handlebar mount on the luggage rail. Solid performance, and I ran a coax jumper out to the SDS100 by the campfire most nights with excellent reception. I've yet to hear back from my ham friend for his opinion, but the 220R gets my vote.

 

[Ubbe]

...but the 220R gets my vote.

What's the dimensions of a 220R? isn't it designed to cover from 220MHz (the name implies it) and upwards and have a dual band top element for 144MHz and 430MHz? If VHF air are interesting then it might be suitable with a bigger discone that covers from 100MHz and upwards? The lenght of the lower skirt/cone elements are very close to a 1/4 wave length of its lowest frequency.

A smaller discone like the 220R will work better at 700-900Mhz compared to a full sized discone.

/Ubbe

 

[JimD56]

I run 2 attic antennas 1) Diamond VHF/UHF Discone 2) 700-800mhz Yagi both into a comet duplexer with a 20-foot drop RG6 into an Electroline +15db preamplifier then into an Electroline 8 way +4db preamp into the rack. No issues, great results.

 

[dlwtrunked]

What's the dimensions of a 220R? isn't it designed to cover from 220MHz (the name implies it) and upwards and have a dual band top element for 144MHz and 430MHz? If VHF air are interesting then it might be suitable with a bigger discone that covers from 100MHz and upwards? The lenght of the lower skirt/cone elements are very close to a 1/4 wave length of its lowest frequency.

A smaller discone like the 220R will work better at 700-900Mhz compared to a full sized discone.

/Ubbe

No, the 220R in the Diamond discone is not specifically a 220 MHz band antenna. Every other cone element appears to be a coil. so it is a combination of a discone with two sorts of cone elements (not readily noted in a photo) and a vertical whip with two loading coil. It is designed to work as 144/904/1200MHz, and 440MHz as well as scanner antenna (note they do not even list it as being a 200 MHz transmit antenna in their literature that I have). I keep one on my desk and had one on the car roof until when working, I pulled into a sensitive DC area government agency parking lot and the security people did not like it.

 

[Ubbe]

Every other cone element appears to be a coil.

That's the ground plane elements for the top whip when the antenna operates as a GP antenna and not for the discone. The mechanical dimensions of the cone and horizontal elements are the actual discones measurements.

The horizontal elements are 80% of a 1/4 wave from tip to tip across the center. If that is 37cm, or 14 inches, then it's designed for 200Mhz and upwards. Shorter than that and its lowest frequency are higher, for the discone part of the antenna.

The top whip are said to be a 1/2 wave at 144MHz and might also work as a 1/4 wave at 75MHz, but that's in a GP operation at tuned frequencies and will perform worse between those two frequencies and the discone are out of the equation.

/Ubbe

 

[bearcatrp]

here are the specs for the 220R...

Diamond® Antenna ~ D220R

I have one. Used it in the house in the winter until I could put a antenna outside in the spring. Works fairly well. Could not pick up airport beacon that constantly transmit information on the airport. My outside discone picks it up. If you have the room for a full size discone in the attic, do that. otherwise the D220R will be the next best thing.

 

[Ubbe]

here are the specs for the 220R...

I've already looked at that and it only says max diameter 8.5" which seems to be the cone elements that goes a bit wider than the horizontal elements. Maybe the horizontal elements are 8" tip to tip at best and then the actual discone design works from 400MHz and upwards. Lower frequencies are completely done by the top whip in a ground plane working mode.

/Ubbe

 

[N1FKO]

So, for limited space in an attic, is a Diamond 220R mini-discone sufficient?

I switched from the 220R on a stick to the the Tram 1410 as described here by JonWienke and had a measurable improvement (my benchmark was local ATIS reception which went from nonexistent to an easily readable signal).