NMO34 with the W640 (64" whip) vs NMO-27 vs CWB-27

[KX4KDH]

The "W" in CW27 is for wideband, the coils are very much different.

Right. I was correcting the 67” whip statement.

 

[KX4KDH]

Can anyone provide data as to:

Relative bandwidth between the NMO34 with the W640 (64" whip) , NMO-27 and CWB-27?

Relative performance between the NMO34 with the W640 (64" whip) , NMO-27 and CWB-27?

Cutting chart for NMO34 with the W640

Availability of the CWB-27?

I can now tell you that the NMO34 with an uncut 64” whip with no spring the center frequency is right at 29.00mhz. 2.0 SWR range is 28.08 to 30.14mhz. That’s on the roof of my crew cab F-350.

 

[mmckenna]

I can now tell you that the NMO34 with an uncut 64” whip with no spring the center frequency is right at 29.00mhz. 2.0 SWR range is 28.08 to 30.14mhz. That’s on the roof of my crew cab F-350.

Here's the NMO-27 on a permanent mount, dead center on the roof of a crew cab F-350. 2:1 SWR is between 26.587MHz and 27.817MHz, give or take. Looks like you picked up about 1MHz of bandwidth with that setup.

 

[RFI-EMI-GUY]

Thanks KX4KDH
I need a smidgen more to span 26.965 to 29.700 (CF: 28.3325 +/- 1.3675 MHz). Maybe a fatter rod? What rod diameter are you using? Measured at base?

 

[KX4KDH]

Thanks KX4KDH
I need a smidgen more to span 26.965 to 29.700 (CF: 28.3325 +/- 1.3675 MHz). Maybe a fatter rod? What rod diameter are you using? Measured at base?

Using .100 diameter whip. That’s all that will fit. I sunk the whip all the way to the bottom of the mount. I may grab an NMO30 base (in the name of experimentation) to see how far down it will move. I’m looking for the same thing you are.

That being said, I’m wondering what adding the spring will net me. Should bring everything down, but I doubt it would bring it down 1mhz.

 

[KX4KDH]

Here's the NMO-27 on a permanent mount, dead center on the roof of a crew cab F-350. 2:1 SWR is between 26.587MHz and 27.817MHz, give or take. Looks like you picked up about 1MHz of bandwidth with that setup.


View attachment 172913

Very interesting. They claim 27-30mhz for that antenna. I do realize there are all kinds of variables. My antenna is more toward the back of the cab. I also have a Larsen NMO450B toward the front for GMRS.

 

[prcguy]

I can now tell you that the NMO34 with an uncut 64” whip with no spring the center frequency is right at 29.00mhz. 2.0 SWR range is 28.08 to 30.14mhz. That’s on the roof of my crew cab F-350.

I can now tell you that the NMO34 with an uncut 64” whip with no spring the center frequency is right at 29.00mhz. 2.0 SWR range is 28.08 to 30.14mhz. That’s on the roof of my crew cab F-350

Using .100 diameter whip. That’s all that will fit. I sunk the whip all the way to the bottom of the mount. I may grab an NMO30 base (in the name of experimentation) to see how far down it will move. I’m looking for the same thing you are.

That being said, I’m wondering what adding the spring will net me. Should bring everything down, but I doubt it would bring it down 1mhz.

I drilled out the whip holder on one of my CW27s and put on a whip about .124" dia at the base. Not for more BW but to make it stiffer. I don't think you'll get any more BW out of an NMO34, that's why Laird and Panorama made WB versions with a fancy coil.

 

[mmckenna]

Very interesting. They claim 27-30mhz for that antenna. I do realize there are all kinds of variables. My antenna is more toward the back of the cab. I also have a Larsen NMO450B toward the front for GMRS.

The antenna is sold as tunable in the 27-30MHz range. It does not say it will cover all of that spectrum.

The NMO34 is designed to cover 34-40MHz with their standard whip. As you've found, you can add a longer whip and change it, but it's still not covering 6MHz.

 

[n3obl]

the range will change based on how short or long the whip is.

 

[RFI-EMI-GUY]

If only we could coat an antenna whip with some sort of thermistor like semiconducting material that would sense voltage nodes and tune as appropriate.

 

[KX4KDH]

The antenna is sold as tunable in the 27-30MHz range. It does not say it will cover all of that spectrum.

The NMO34 is designed to cover 34-40MHz with their standard whip. As you've found, you can add a longer whip and change it, but it's still not covering 6MHz.

This is absolutely correct. Sometimes I am a complete boob and forget this is not the range of the antenna, but rather the tunable range of the antenna.

 

[mrweather]

That being said, I’m wondering what adding the spring will net me. Should bring everything down, but I doubt it would bring it down 1mhz.

Adding a spring will have the effect of lengthening the whip, but it's not 1:1. It will also broaden the bandwidth a little (reduces the Q of the antenna).

The Larsen spring is about 3" tall. I'd say give it a try using the existing W640 whip and see how far that drops the resonance frequency.

 

[slowmover]

Adding a spring will have the effect of lengthening the whip, but it's not 1:1. It will also broaden the bandwidth a little (reduces the Q of the antenna).

The Larsen spring is about 3" tall. I'd say give it a try using the existing W640 whip and see how far that drops the resonance frequency.

Either found no length given, or 4.1” or 6.1”http://forums.radioreference.com/th...-whip-vs-nmo-27-vs-cwb-27.480630/post-4083876

PulseLarsen SPRINGB

Black Stainless Steel Shock Spring for Larsen Antennas

www.hamradio.com

.

 

[KX4KDH]

Either found no length given, or 4.1” or 6.1”NMO34 with the W640 (64" whip) vs NMO-27 vs CWB-27

PulseLarsen SPRINGB

Black Stainless Steel Shock Spring for Larsen Antennas

www.hamradio.com

.

I also found a .125” 66” whip on Amazon. Probably Chinese, but what isn’t these days?

 

[mrweather]

Broke out the tape measure and my Larsen spring (SPRINGB) is 2.5" long.

Looked up some cutting charts from an old Larsen Antenna SourceBook and inserting a spring reduces whip length anywhere from just under 1" to almost 3" depending on frequency of the base coil.

 

[slowmover]

Broke out the tape measure and my Larsen spring (SPRINGB) is 2.5" long.

Looked up some cutting charts from an old Larsen Antenna SourceBook and inserting a spring reduces whip length anywhere from just under 1" to almost 3" depending on frequency of the base coil.

“Reduces” (freq spec), or, one needs to reduce height (length) to maintain original tune?

Thanks for measurement.

Reading a post elsewhere stated that TOTAL height from roof including mount was 70” with NMO34 & W640 whip prior to any cut. Spring would then bring that to 72.5”.

.

 

[RFI-EMI-GUY]

 

[slowmover]

*Antenna Tuesday* Colorado WB Specification

Antenna Tuesday this time! Konektor5000 in Poland, Masa in Japan and Pieter in the Netherlands have messaged me, whatsapp me and Facebook messaged me about what appears to be an “updated&#822…

simonthewizard.com

.

 

[KX4KDH]

The only thing I don't like about this one is it brings us right back to a short whip. But I am starting to like it just because of what it can do.

Apparently Laird has a 10/11m antenna that is wide band:

C27S: CB Radio & 10M Whip Antenna for 27-31 MHz with Spring Base. Equivalent to 102 Inch Whip Antenna.

The Laird - Antenex C27S is a 1/4 wave, unity gain CB radio antenna that is tunable for CB frequency range (26.965 - 27.406 MHz) and 10 Meter range ( 28 MHz - 29.7 MHz). This antenna comes with spring base which provides increased flexibility, better shape retention, and eliminates electronic...

www.arcantenna.com

 

[RFI-EMI-GUY]

*Antenna Tuesday* Colorado WB Specification

Antenna Tuesday this time! Konektor5000 in Poland, Masa in Japan and Pieter in the Netherlands have messaged me, whatsapp me and Facebook messaged me about what appears to be an “updated&#822…

simonthewizard.com

.

I have to know if the graphite whip is a resistive element or simply a support for a radiating wire, perhaps spiral? So far no reception reports.