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

[RFI-EMI-GUY]

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?

 

[niceguy71]

I know nothing about this stuff..... But I was thinking if the cb27 coil and 49 inch whip are mated for each other..... Than putting a 64 inch taller whip on it would require cutting ... And if I cut a 1/4 inch at a time.... I'd be afraid it would need to be cut until it was the 49 inches ...... Just like Larsen intended it to be???

 

[KX4KDH]

I actually ran this setup (NMO34 with 64" whip) for 10M FM use. It was flat across a surprisingly wide bandwidth. I can't recall off hand. However, I will be putting it back to use as soon as my Quad6 Pro shows up.

No cutting was done to the whip.

 

[prcguy]

The CW27 is impressively wide and will cover from below CB to above 10m with a good match and still put out a big signal. In my experience a simple base loaded NMO will be hard pressed to exceed 500KHz before the match gets wonky. Even if you could get 1Mhz out of it the CW27 will be much better.

 

[RFI-EMI-GUY]

I know nothing about this stuff..... But I was thinking if the cb27 coil and 49 inch whip are mated for each other..... Than putting a 64 inch taller whip on it would require cutting ... And if I cut a 1/4 inch at a time.... I'd be afraid it would need to be cut until it was the 49 inches ...... Just like Larsen intended it to be???

My intent is to compare : NMO34 with the W640 (64" whip) vs NMO-27 vs CWB-27 (The latter two with standard whips)

 

[RFI-EMI-GUY]

The CW27 is impressively wide and will cover from below CB to above 10m with a good match and still put out a big signal. In my experience a simple base loaded NMO will be hard pressed to exceed 500KHz before the match gets wonky. Even if you could get 1Mhz out of it the CW27 will be much better.

Do you mean the CWB-27 is impressively wide? Do I have the correct nomenclature?

 

[RFI-EMI-GUY]

I actually ran this setup (NMO34 with 64" whip) for 10M FM use. It was flat across a surprisingly wide bandwidth. I can't recall off hand. However, I will be putting it back to use as soon as my Quad6 Pro shows up.

No cutting was done to the whip.

I would be interested in your results, VSWR at spots at ends and middle as well as vehicle mounting specifics.

 

[prcguy]

My intent is to compare : NMO34 with the W640 (64" whip) vs NMO-27 vs CWB-27 (The latter two with standard whips)

Of the three mentioned I only have Laird CW27 which is the chrome version of the CWB27 which is black. This is the wide band 26.8 to 29.7MHz with no tuning and 67.5" whip. If you put the 67.5" whip on a Larsen NMO34 coil it will work a little better than a stock Larsen NMO27 with 49" whip and depending on how long the whip is after tuning it may equal or slightly out perform a CW27 wide band. Not sure if the CW27 series has any or much loss due to the complicated circuit in the base and that's what might give an edge to the long whip NMO34.

 

[RFI-EMI-GUY]

Of the three mentioned I only have Laird CW27 which is the chrome version of the CWB27 which is black. This is the wide band 26.8 to 29.7MHz with no tuning and 67.5" whip. If you put the 67.5" whip on a Larsen NMO34 coil it will work a little better than a stock Larsen NMO27 with 49" whip and depending on how long the whip is after tuning it may equal or slightly out perform a CW27 wide band. Not sure if the CW27 series has any or much loss due to the complicated circuit in the base and that's what might give an edge to the long whip NMO34.

That explains my confusion. I thought the CWB was a wideband coil with the setscrew glued with loctite. Very hard to sift through the on-line specs.

 

[prcguy]

My truck is not ideal for getting the best out of a CW27 due to mounts on the edge of the hood and one on the upper bed wall behind the cab. Years ago I measured one hard center mounted on a large truck roof and it matched up as advertised from below the CB band to the upper end of 10m. It also radiates really well.

 

[prcguy]

That explains my confusion. I thought the CWB was a wideband coil with the setscrew glued with loctite. Very hard to sift through the on-line specs.

The CW27 whip comes off easy with set screws, I upgraded one with a thicker whip where I had to drill out the whip adapter. The thicker whip is on the left in the picture below. These two CW27s are under the Antenex brand before being bought up by Laird and whoever owns them. I actually have three of these antennas, just thought I would add that so you can see what an @hole I am....

 

[niceguy71]

My intent is to compare : NMO34 with the W640 (64" whip) vs NMO-27 vs CWB-27 (The latter two with standard whips)

I'm very interested in your results...... can't wait to see how it works out.

 

[RFI-EMI-GUY]

The CW27 whip comes off easy with set screws, I upgraded one with a thicker whip where I had to drill out the whip adapter. The thicker whip is on the left in the picture below. These two CW27s are under the Antenex brand before being bought up by Laird and whoever owns them. I actually have three of these antennas, just thought I would add that so you can see what an @hole I am....

View attachment 172066

You are hoarding! I see the CW27 on Digikey as obsolete and a CB27 shown for $94 now. The catalog does not show that antenna. It has a 49 inch whip so probably narrow band.

 

[prcguy]

You are hoarding! I see the CW27 on Digikey as obsolete and a CB27 shown for $94 now. The catalog does not show that antenna. It has a 49 inch whip so probably narrow band.

Yes I'm hording and I'll do it again. I was trying to find an old picture of the coil innards and cant find a close up but its impressive with a couple of little toroid coils and high RF current mica caps. The 49" whip models are cut to frequency narrow band and I've only seen the 67.5" whips on the WB models including the 39-46MHz version that CHP bought for years. That was the Laird WPC39SOB-001 with newer designed larger coil.

Here is a partial spec sheet on the CW27.

 

[RFI-EMI-GUY]

I get it. If I find a source, I will probably have to buy a spare. one is none, two is one, three is a spare.

 

[prcguy]

I get it. If I find a source, I will probably have to buy a spare. one is none, two is one, three is a spare.

Now you got it. My motto in life is some is good, more is better and too much is just right. I have my fill so corner the market!

 

[slowmover]

Of the three mentioned I only have Laird CW27 which is the chrome version of the CWB27 which is black. This is the wide band 26.8 to 29.7MHz with no tuning and 67.5" whip. If you put the 67.5" whip on a Larsen NMO34 coil it will work a little better than a stock Larsen NMO27 with 49" whip and depending on how long the whip is after tuning it may equal or slightly out perform a CW27 wide band. Not sure if the CW27 series has any or much loss due to the complicated circuit in the base and that's what might give an edge to the long whip NMO34.

Rated by manufacturer to 200W.
Run something adjustable to peak about 150W at 50% or less, but stay half of that for GP otherwise.

.

 

[n3obl]

I had a dealer use a higher freq coil with a longer whip then stock to make a wider bandwith antenna. You will need to do some trial and error. I had one setup to give me a low swr across all of 33.xx mhz.

 

[prcguy]

I had a dealer use a higher freq coil with a longer whip then stock to make a wider bandwith antenna. You will need to do some trial and error. I had one setup to give me a low swr across all of 33.xx mhz.

That usually doesn't widen the BW noticeably but it does make for a more efficient antenna with a little more gain.

 

[mrweather]

Relying less on the loading coil and more on the whip length is a good thing.