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Portable: 16' Extendable Mast/Tripod/Antenna 11 years 11 months ago #78

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Connecticut is “Line of Sight Challenged” with its North-South ridges. :(

You have probably noticed the range limitations of using a "rubber duck" antenna on your HT.
It does get frustrating, doesn't it?
- I know... I speak from personal experience.

However, for anyone looking to improve portable VHF/UHF operations, here is a way to get more range. I have included photos (below) to show you Ed's (WA1LEI) example.

Harbor Freight Tools
16' Masts ALL GONE! - ONLY 20' FLAGPOLES ARE BEING SOLD NOW.(Sept. 2013)
If you can still find them, Harbor Freight stores are now discontinuing the 16’ telescoping “Flag Poles (with flag) and they are going FAST.
- The 20’ (2 flag) model sells regularly for $69.99

WARNING:
These flagpoles are ONLY good for TEMPORARY USE.

- If you leave them outside too long, you run the risk of corrosion. This makes the slip joints near impossible to loosen and retract the pole (BTDT).

In the photo below, we see looking from the ground and going up:
• Black Speaker Stand (Tripod),
• White PVC pipes filled with sand*
• 16’ Mast
• The lower section of a 144/440 MHz Base Antenna (Gain) and Coax.

COAX:
While everybody knows about LMR-400 as being the entry level and preferred coaxial cable for VHF/UHF feed-lines, I deem it too fragile for field use.

Better to consider using a "CJ-BF" Low-Loss Bury/Flex coax cable (1/2" diameter).
- similar to LMR-400, but less delicate.

Anything less (e.g. RG-8x) is a decibel (i.e. Signal) losing proposition at these frequencies (VHF/UHF)

HOW MUCH COAX?
With an antenna feedpoint at 20' above ground, that leaves 25 feet of coax to run to your radio plus 5 feet allowing for floor to table rise.
Consider THIS:
Have 2 lengths of 50' of Low-Loss Flex/Bury coax AND with a barrel connector (to connect them) in your GO KIT.
- This will give you versatility and options depending on distance from the radio to the antenna.

*For peace of mind, although quite stable in a "slight" breeze, you might want to put 3 stakes in the ground with 3 guy ropes attached to the mast for safety, and/or consider placing sandbags on each of the three legs of the tripod.

UPDATE: June 5, 2023
I am now using a Drive On Mast Mount to use with the Telescoping Flag Pole/Mast.
It is easier (and safer) for 1 person to set up than using the tri-pod.
Photo to follow.

Regards,
Douglas Sharafanowich
District Emergency Coordinator, Region 2
Connecticut Amateur Radio Emergency Service (CT ARES)
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Re: Portable: 16' Extendable Mast/Tripod/Antenna 11 years 10 months ago #97

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Antennas:
You want Mobile and Portable antennas that can take you the distance on VHF/UHF Simplex

Mobile Antennas (For the Car/Truck)
Forget the of the small Hershey Kiss style antennas!
Consider any of these:
Jetstream: JTM3B
Comet: CA-2x4SR , or CSB-770A (best gain)
Diamond: NR770HB

Portable Antennas (for temporary set-up in the field with a mast*)
Any “Gain” antenna that is around 5’5” (for easy transport and set-up)
Consider any of these:
Jetstream: JTB3B
Comet: GP-3
Diamond: X50A

* Note: I am using a Telescoping Flag Pole (Harbor Freight Tools) as my mast.
I have the option to: Tie it to a fence post, Mount it on a speaker tripod, or Slide it into a Drive-On Mast Mount.

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Re: Portable: 16' Extendable Mast/Tripod/Antenna 11 years 10 months ago #99

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I assembled my version of this tripod/mast/antenna on Saturday, and used it with my 5 watt HT at the Net Control Station (NCS) supporting the Parent Child Resource Center Ride on Sunday. :)

Don't forget to remove the flag mounting hardware.
Just remove the top tube's center insert (two screws in the side of the tube) and slide off the flag mounting hardware. Then, put the center insert back in the top tube and replace the 2 securing screws.

For a finished look add a neoprene washer and hex bolt to the center insert's threaded shaft where the Truk (a round ball at top of the flag pole) would have screwed in.

I did make one substitution:
For the antenna, I used an equivalent 5'+ Comet Dual Band Antenna (GP-3) ... because everybody within driving distance was out of stock last week on the Jetstream JTB3 antenna.
- Another recommended antenna is the Diamond X50A.

PS:
While doing more research, I found that these antennas are now made in 1 piece (plus the 3 radial stubs).

The good news is that you don't have to fiddle with putting two shafts together in the field.

The bad news is that you now have a 6 foot piece to put into the car for transport, instead of two 3 foot pieces.
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Re: Portable: 16' Extendable Mast/Tripod/Antenna 11 years 9 months ago #105

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I now understand that the 16' extendable flag poles are no longer in stock. :( :oops: :whistle: :S :(

However, they still sell the 20' version (with mounting hardware for 2 flags) at a cost of just under $50.

I have heard that KB1YCA is using this 20' version successfully :) :woohoo:
WE WANT PICTURES! B)

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Re: Portable: 16' Extendable Mast/Tripod/Antenna 11 years 9 months ago #107

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COAX STRAIN RELIEF
One of the issues that you might want to consider is how to provide strain relief for the heavy 1/2" coax and its fitting at the antenna.

I saw how David K1DAV (CTARES-R5 DEC) and his crew makes a single loop of the coax from the antenna fitting and has it passing through a tie-wrap (?) secured to the top of the mast they use.

This takes the downward pull off the coax fitting at the antenna and transfers it to the attachment [tie-wrap(?)] at the top of the mast for the downward run.

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Re: Portable: 16' Extendable Mast/Tripod/Antenna 11 years 9 months ago #108

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QUESTION
"Douglas, why are you using such a heavy coax like LMR-400ow Loss type of coax? (I use the Low Loss Bury/Flex version)."

ANSWER
Because I can't afford LMR-600 (Flex)! :P ;)

But seriously...
Our goal is to MAXIMIZE the amount of SIGNAL we can SEND and HEAR... and still be portable.

Therefore, we need to MINIMIZE the SIGNAL LOSS between the radio and the antenna.

At 150 MHz (~ 2m band)
The Low Loss Bury/Flex coax has a published loss of 1.8 dB per 100 feet.

At 450 MHz (~ 70 cm/440 band)
The Low Loss Bury/Flex coax has a published loss of 3.1 dB per 100 feet.

ASSUMPTION
Signal loss is "linear" over distance.

50' Comparisons: 150 MHz / 450 MHz
Low Loss Bury/Flex
0.9 dB / 1.6 dB

RG-8x
2.3 dB / 4.1 dB

RG-58
2.8 dB / 5 dB


Hope this clarifies why we recommend the Low Loss Bury/Flex for portable use.

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