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Reviews Categories | Antennas: HF: Yagi, Quad, Rotary dipole, LPDA | MFJ-2275 Single-band Rotatable mini-Dipole Help


Reviews Summary for MFJ-2275 Single-band Rotatable mini-Dipole
MFJ-2275  Single-band Rotatable mini-Dipole Reviews: 2 Average rating: 3.5/5 MSRP: $$49.95
Description: Rotatable, lightweight, isolated mini-dipole. Includes an MFJ-347 isolated mini-dipole mount and two HF sticks of your band choice; ie. 75m is p/n MFJ-2275 and includes two MFJ-1675T Mobile Ham-tenna(TM) whips.
Product is in production.
More info: http://www.mfjenterprises.com/Product.php?productid=MFJ-2275
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You can write your own review of the MFJ-2275 Single-band Rotatable mini-Dipole.

N3ZOC Rating: 4/5 Feb 11, 2015 13:32 Send this review to a friend
Was successful in modifying to operate on 80m.  Time owned: more than 12 months
Reference my initial review several years ago when I lowered the resonant frequency for 80m at about 3550 kHz.

I recently had a query about my use of this antenna on 80m instead of 75m. There was some confusion over the terminology I used to describe sections of the antenna.

When I stated ".....where the whip adapter screws into....." in the last sentense of my query on eham.net, I was referring to the metal adapter which has two hex head set screws which hold the lower section of the stainless steel uninsulated silver colored (whip, wire, or what ever you want to call it) that extends out to a ball-tip static discharge point (the extreme end of the antenna opposite of the antenna feed point). This is the section of the antenna which is on the opposite end of the loading coil from the feed point.

I lowered the resonant frequency of the antenna (stick) by adding several inches of length to the "whip" half of the antenna where it connects the two halves of the antenna (the base/loading coil half to the outer half (the flexible stainless steel?) wire/whip/rod/whatever .

In other words:

1. Loosen the two hex head set screws and extend the "whip" as fully outward as possible while maintaining the ability to hold it in place with the set screws re-tightened.
2. Unscrew and remove the adapter (having two set screws)and the whip from the section with the loading coil.
3. Insert a 3/8-24 nale/female standoff (must be hollow) where the adapter was removed.
Note: More than one standoff may be needed to lower the resonant frequency sufficiently to meet your requirements. I needed two 1-1/2 inch standoffs.
4. Install the adapter and whip removed in step 2 to the added standoff.
5. Measure the resonant frequency.
6. Repeat steps 2-5 above, adding additional standoffs between the coil half of the antenna and the adapter (holding the "whip" with set screws), until you obtain a resonant frequency at or below your lowest intended operating frequency.
7. You can now increase the resonant frequency by loosening the set screws and moving the "whip" to a shorter position.

Other solutions:

Obtain a stainless steel whip longer than the one supplied with the original antenna (which I could not find).
Caution: The whip should not be so long such that it will extend down into the loding coil when adjusting its length using the set screws or it may cause the coil to overheat.

Adding a short length of conductive wire to the tip of the whip (which I could not devise a reasonable method of accomplishing).

Please excuse any errors in this as I am having to use screen reading software because of limited vision.
73, Frank, N3ZOC
 
N3ZOC Rating: 3/5 Jan 1, 2009 14:10 Send this review to a friend
Unanswered specification was in the box.  Time owned: 0 to 3 months
After several emails to MFJ asking if this antenna would tune the CW portion of 75/80m with no response from MFJ, I telephoned them for tech support and got referred to three different departments including the MFR across the street. None of them could tell me if the MFJ-2275 would tune 3500-3600 kHz.

Posted a stray on eham with no replies.
Finally added it to my Xmas list and it arrived from R&L. Opened the box, removed the instruction sheet from the plastic bag and low and behold the very first sentence states:
(QUOTE)
These HF antennas are designed to operate over the phone portion of HF bands with a typical VSWR of 2:1.
(UNQUOTE)
I can only guess that the folks at MFJ cannot read the "MFJ Instruction Manual".

Because I operate 99.99% CW on HF, I wanted this as an extra receive antenna to null out any directional interference and assist in copy of stations during my stints as NCS on traffic nets.

Now I am trying to figure a way to extend the lower section several inches with a hollow M/F 3/8-24 where the whip adapter screws into it which will lower the resonance.

A very disappointed Ham,
Frank O,
N3ZOC
 


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