Larsen NMOWB150 question (NMO airband antenna advice)

[cbehr91]

If I'm reading the cutting chart correctly the antenna whip comes from the factory at a length considerably longer than the lowest frequency range in the cutting chart, which is 136 MHz and up. I'm aware of the Larsen NMO118, which is a 5/8 wave, but its bandwidth is too narrow to cover the entire airband. My two questions are:

1.) Do any of the antenna gurus know if the NMOWB150 would work ok for the airband at its factory length of 51.5" (perhaps a spring could help broaden the useable range even more).
2.) Might a longer whip like the Larsen low band whip work better? I'm fine with Frankensteining an antenna+spring+coil.

I could also post the frequencies of the local airport I recently moved close to if that helps.

 

[prcguy]

No matter what you do the Larsen 5/8 is only going to have several MHz of useable bandwidth then performance will start to drop off. I've used the Larsen wide band 1/4 wave with spring and a longer whip for aviation and also the old Antenna Specialists wide band 1/4 wave, the one with a cone shaped spring and with a longer whip.

 

[cbehr91]

No matter what you do the Larsen 5/8 is only going to have several MHz of useable bandwidth then performance will start to drop off. I've used the Larsen wide band 1/4 wave with spring and a longer whip for aviation and also the old Antenna Specialists wide band 1/4 wave, the one with a cone shaped spring and with a longer whip.

Ok, I'll have to do that. I have a wideband Larsen 1/4 wave with spring I have no problem Frankensteining with a longer whip (that part I'll have to purchase). I know some of Larsen's models get muddled, but the Larsen NMOWB150 is 1/2 wave, not 5/8 like the regular NMO150.

 

[tvengr]

ICOM has two VHF aircraft band mobile antennas: K220A with mag mount and K220C with NMO mount.

 

[cbehr91]

ICOM has two VHF aircraft band mobile antennas: K220A with mag mount and K220C with NMO mount.

Interesting. It looks like the old A/S wideband 1/4 wave mentioned in prcguy's post. I guess ICOM found some surplus stock?

 

[mass-man]

are you planning on listening only to airband?

 

[cbehr91]

are you planning on listening only to airband?

With this antenna, yes.

 

[wyomingmedic]

It works just fine as an airband receive antenna, even when cut for 2 meters. Our state runs NMO150WB antennas for all of the state troopers because they work so well. They will cover ALMOST 20mhz under a 2:1 SWR. I generally cut mine for 150mhz and it will cover down into 2m, but also allow me to work on the 160mhz trunking stuff (Motorola radio, state trunking ID; nobody has to get their underwear in a wad).

I have used them on scanners for years as well and they do a great job of airband receive.

 

[FKimble]

Here a cut from the Pulse-Larsen ant book. The WWB150 is a wide band antenna.

Frequency Gain Height Rating Whip Cable
Model Type (MHz) (dBd/dBi) (In) (Watts) Color Assembly/Mount
NMOWB150B Wideband 1/2 λ 135-174 0/2 51.75 100 Black Order Separately
NMOWB150C Wideband 1/2 λ 135-174 0/2 51.75 100 Stainless

Frank

 

[cbehr91]

I ended up installing a 20.5" whip from an NMO ground plane kit into the wideband 1/4 wave Larsen cone and spring. I haven't had a chance to test it out yet. I'm only about four miles as the crow flies from KCLE, but would still be monitoring while mobile.