Low-band indoor antenna options

[Anderegg]

Currently working with NMO mount, and various telescoping things and a long OEM Moto rubber duckie, but looking for what would work best in an apartment. I have a BNC low-band Unication wire antenna I an deploy, the previously mentioned low band NMO whips, but simple logic such as put it in the window for best RX doesn't pan out. (windows are not RX inhibiting) Against a back wall, floating in the middle of the room, on the floor, it is just hit and miss and the hand -on-antenna effect makes testing locations problematic.

For the wire option, should I string around a window, should it stay straight, vertical, horizontal, around the window, diagonal across the wall, strung from a lamp to my TV...any tips as to what should work best would be appreciated.

Paul

 

[prcguy]

What is the building made with, stucco, concrete, wood or plastic siding? Stucco is bad with a metal lath shield under the crust. Concrete has metal and rebar, not so good. Wood or plastic siding has some hope but most modern windows will have metal flashing all around them. You also have wiring running through the walls. In a wooden place I would think an outside wall away from a window that has no wiring would be best for VHF lo. And keep the antenna far away from computer equipment and switching power supplies.

I have details on a military designed broad band whip that seems easy to fabricate and when I find the details I can post it. I remember it had a 4:1 balun, easy to make, then an insulated pole about 7ft long and a wire that ran the full length then doubled back for about 2ft with some spacing between wires. It needs a ground plane and if placed against a wall you could run some wires heading away from it in opposite directions against the wall.

 

[tweiss3]

In for recommendations. I've just started thinking about VHF Lo, and options for attic seem limited.

 

[John_S]

What with the solar activity on the rise, I've been thinking about giving Low band some attention...again. Early 90's was the last effort and found some cool DX. In those days, I made a fan dipole with 3 dipoles IIRC. I think I split the band in 3 sections and calculated dipole lengths and ran all 3 to a coax feedpoint. I'm also thinking maybe concentric loops with the same approach. Tough to try and cover that much bandwidth with a simple antenna.

 

[HappilyRetired]

Currently working with NMO mount, and various telescoping things and a long OEM Moto rubber duckie, but looking for what would work best in an apartment. I have a BNC low-band Unication wire antenna I an deploy, the previously mentioned low band NMO whips, but simple logic such as put it in the window for best RX doesn't pan out. (windows are not RX inhibiting) Against a back wall, floating in the middle of the room, on the floor, it is just hit and miss and the hand -on-antenna effect makes testing locations problematic.

For the wire option, should I string around a window, should it stay straight, vertical, horizontal, around the window, diagonal across the wall, strung from a lamp to my TV...any tips as to what should work best would be appreciated.

Paul

You can do what I'm doing. Go to Multec Communications / RFwiz.com I Communications and Electronics Specialists and purchase an Austin Spectra that covers 30-50, 150 - 174, and 700 and above. That step woman. Step two is to get their forefoot antenna sleeve. It has an nmo mount on top of it and a so239 on the bottom of it. It's basically a 4-ft extension that using a miniature Christmas tree base you can simply mount in the corner of your room and get all band coverage. This is not a cheap solution. It will cost you $298 plus tax and shipping. If you do not need low bands you can get a cheaper antenna like a PCTel or a ComTelco as well as the 4 foot sleeve from RF quiz and stand it in the corner.

 

[prcguy]

You can do what I'm doing. Go to Multec Communications / RFwiz.com I Communications and Electronics Specialists and purchase an Austin Spectra that covers 30-50, 150 - 174, and 700 and above. That step woman. Step two is to get their forefoot antenna sleeve. It has an nmo mount on top of it and a so239 on the bottom of it. It's basically a 4-ft extension that using a miniature Christmas tree base you can simply mount in the corner of your room and get all band coverage. This is not a cheap solution. It will cost you $298 plus tax and shipping. If you do not need low bands you can get a cheaper antenna like a PCTel or a ComTelco as well as the 4 foot sleeve from RF quiz and stand it in the corner.

The Austin Spectra does cover a narrow range in the VHF lo band and works ok for its size but its VHF/UHF and 800 performance is not that great compared to commercial multiband antennas from Larsen, Laird, PCTEL and others. The sleeve ground thing for the Spectra is a joke and if you search RR you should find people complaining how bad that version works.

I have had two Austin Spectras here for many years and after initially trying them out I've never put them to use because other antennas work better.

 

[HappilyRetired]

That's odd. I've read just the opposite. But okay. What all band antenna do you recommend that includes 30-50 mhz? What I was shopping for an antenna this group highly recommended the Spectra.

 

[John_S]

Part of the issue is that antennas tuned for multiband use are no where near the size needed for low band tuning. Really need a dedicated antenna. If you're totally stuck with installing something indoors, I would try a basic loop made from hook up wire. A 6' square loop could be thumbtacked to a wall and would roughly give reception broadsided to the loop in either direction. Being in close proximity to the wall will change the tuning and pattern to some extent. In free space, those dimensions will give around 40 mHz tuning. Another approach is to take about 25' of hook up wire and fit a loop shape to what fits in the room. The larger the included area in the loop the better. Practically any antenna near full sized for the desired frequency will work better.

 

[MUTNAV]

Um... Just to be clear, when "Low band" is mentioned is this thread and Forum (scanner and Receiver antennas), are we talking low VHF or Low as in below MW?

Thanks
Joel

 

[HappilyRetired]

I am looking at picking up a Larsen NMO40C that covers 40-50. Austin Antenna makes a 4-ft extension with an NMO on one end and an SO239 on the other. Using a small platic Christmas tree stand I can stick it in the corner. I'm trying to find a decent multi-band antenna for 150 on up and I'll do the same with it. The property owner won't let me put an antenna up on the roof. This is my office and at home I have separate antennas for each band. I use a triplexer to connect them to a multi-coupler and then feed the other radios that way. I can't do that here though. I'll give it a try to the loop you suggested. I want this for dedicated CHP and they're kind of in a 360 around me. But I'm willing to try new things. Thank you for the suggestion. I'm new at this.

 

[HappilyRetired]

Um... Just to be clear, when "Low band" is mentioned is this thread and Forum (scanner and Receiver antennas), are we talking low VHF or Low as in below MW?

Thanks
Joel

I'm new at this and I don't know the lingo. All I can say is low band as in VHF low band 30-50. The only thing below that I'm aware of is CB radio and I sure don't want to do that.

 

[MUTNAV]

I'm new at this and I don't know the lingo. All I can say is low band as in VHF low band 30-50. The only thing below that I'm aware of is CB radio and I sure don't want to do that.

got it... I was just wondering because some of the antenna sizes that are being talked about would be ok for a Low frequency antenna with an amplifier if limited to indoor use.

https://www.arrl.org/files/file/Technology/tis/info/pdf/0109031.pdf

etc...
and when others mentioned stringing a wire up around a room, that sounded like a lower frequency thing also.... in addition, when someone else mentioned solar cycles and DX it got me to wondering.

Thanks

 

[John_S]

Yup...VHF low band...generally considered 30-50 mHz. Because of it's location in the RF spectrum, it can exhibit behavior from the upper HF bands like 10 and 12 meters...and also show behavior like 6 meters and higher. This is part of why this area is so interesting to monitor. Loop antennas can be very functional on almost any band...right up into UHF and higher. The standard formula is 1005/freq in mHz. Feedpoint can be in a variety of places. A 2:1 rectangle will have a 50 ohm feedpoint impedance when fed in the center of one of the short sides.

 

[prcguy]

That's odd. I've read just the opposite. But okay. What all band antenna do you recommend that includes 30-50 mhz? What I was shopping for an antenna this group highly recommended the Spectra.

The only similar antenna to the Austin Spectra is the old Antenna Specialists MON series which I prefer. Look at the chart in the attached article I did for Monitoring Times Magazine which shows the gain of those two antennas referenced to a wide band military antenna. This article used to be posted on RR somewhere but I can't find it, so here it is again.

The A/S has much wider band width on VHF low compared to the Spectra, but neither cover the entire 30-50MHz range without serious degradation. They are similar within the VHF hi band then the A/S is much better in the 406-470 range where the Spectra gets better between about 475 and 512MHz. That particular test did not include 700-800MHz so I don't know which one is better there but I suspect the A/S is.

The factory ground plane kit used on the base station version of the A/S MON series works well and provides a good match for transmitting where the long tube ground thing for the Spectra does not. Otherwise I don't know of any other consumer type antenna similar to an Austin Spectra specifically tuned for VHF lo, VHF hi, UHF and 700/800MHz.

A typical scanner Discone is good for about 118 to 512MHz then the radiation pattern points upward and 700-800MHz suffers greatly on the order of 10dB loss. The ones advertised for 25-1300MHz with a whip on top do the same roughly 118-512MHz fine and the whip resonates very sharply around 50MHz then drops way off anywhere else. You can add a longer whip and center the sweet spot around 42MHz to perk up CA CHP, I've done that and it works ok but its still very narrow band and doesn't cover the entire 39-46MHz range used by the CHP that well.

If you want ok predictable performance across the entire 30-512MHz range with really good VHF lo performance then get the Shakespeare military whip mentioned in the linked article. But its about 9ft tall and may not fit indoors, plus it needs lots of ground plane under it. They are also very pricy new and probably at least $250 for a nice used specimen.