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eHam Forums => Antennas and Towers and more => Topic started by: ZS5WC on March 28, 2016, 10:52:52 AM



Title: Anybody try this "Moregain" 80 & 160m antenna?
Post by: ZS5WC on March 28, 2016, 10:52:52 AM
 ???
This is quite an interesting design-overall length same and shorter than 80m dipole..

http://www.qsl.net/va3iul/Antenna/Wire%20Antennas%20for%20Ham%20Radio/97-Morgain-Dipole_Antenna_160m-80m.jpg

Wonder how it performs on 160m?.

73 de William
ZS4L / ZS5WC


Title: RE: Anybody try this "Moregain" 80 & 160m antenna?
Post by: W4OP on March 28, 2016, 11:41:39 AM
I would expect it to perform identically to an 80/160 trapped dipole.

Dale W4OP


Title: RE: Anybody try this "Moregain" 80 & 160m antenna?
Post by: W2BLC on March 28, 2016, 01:27:08 PM
The Morgain antenna was quite popular in the 70s and 80s. It was about half the length of a dipole for the same frequency. I knew several ops that had them and they were a reliable antenna for 75 and 40 (guess you could do the CW end also if tuned for it).

I never saw a version for 160 meters.

The company has long been out of business.

Here is a link to a PDF on my website that may be of some help.


Title: RE: Anybody try this "Moregain" 80 & 160m antenna?
Post by: K0RS on March 28, 2016, 02:47:53 PM
My first antenna was a Morgain dipole for 40 and 20m.  Given to me by my Elmer.  1964!


Title: RE: Anybody try this "Moregain" 80 & 160m antenna?
Post by: K7MEM on March 28, 2016, 04:40:09 PM
Except for the shorting stubs, that antenna is described in the ARRL Antenna Handbook, 18th Edition. There was also an article in Volume 5 of the Antenna Compendium by John Stanford, NN0F. It is refered to as a Linear Loaded Dipole and say that the shortening doesn't significantly affect the efficiency.

The lengths are right for 160 meters so my guess is that the shorting stubs are used to resonate the antenna on 80 Meters.


Title: RE: Anybody try this "Moregain" 80 & 160m antenna?
Post by: W4OP on March 28, 2016, 05:09:53 PM
There is no free lunch and linear loading is not any better (and may be worse) than lumped element loading. So, the gain will be less than a full length  dipole and the bandwidth will also be considerably less.

Dale W4OP


Title: RE: Anybody try this "Moregain" 80 & 160m antenna?
Post by: KK4OBI on March 28, 2016, 07:20:11 PM
Interesting antenna.  At 1/2 wavelength feedpoint height using #14 wire, it models to give 81 Ohms at 1.6 SWR50.  Gain is 7.7 dBi (Slightly better than a dipole). Radiation is 30 degrees up from horizontal.  Vertical beam width is 30 degrees.  Lateral beam width is 90 degrees.  All this is identical to a dipole. The resonance dip looks very ordinary... not wide, not narrow.  It is an elaborate half-wave dipole.

Since there is a weak resonance at 160 meters, perhaps the "short circuit straps" are related to enhancing this.  There is no easy way to model them.  There must be 6 more wires added and I am going to bed now.  Maybe tomorrow.


Title: RE: Anybody try this "Moregain" 80 & 160m antenna?
Post by: ZS5WC on March 29, 2016, 11:21:13 PM
 :)Wow! , Thanks for the interesting responses!..
I look forward to hearing more about the modelling of this antenna on 160m!.

Quite keen to try it as the sunspots are declining, and want to promote activity on 80 and 160m in ZS.
Most property lots are now small, so it is preventing Hams from erecting of full sized 160m and even 80m antennas.
I have the space, but need to convince the ZS hams that 80 and 160m are very good bands-IF the QRM is low.

I have worked 80m MID DAY recently over the shorter distances -up to 300kM and signals were low but steady. ( 40m was closed on the short skip.)

73 de William
ZS4L / ZS5WC


Title: RE: Anybody try this "Moregain" 80 & 160m antenna?
Post by: KK4OBI on March 30, 2016, 07:01:05 AM
William,

Comparing the antenna models without and with the "short circuit straps" (jumpers) confirms that they are for tuning the 160 meter resonance. Using the 300 cm point (3 meters) specified by va3iul, the resonance was under 1.7 mHz as a harmonic of 3.86 mHz. Step-wise increases in jumper position (3, 4, 5 meters...) progressively raised the harmonic to 1.84 mHz at 3.5 SWR with the jumpers set at 5.7 meters from the ends.  Tuner needed.

As the jumper changes were made, the characteristics of the 3.68 mHz resonance remained about the same at 78 Ohms impedance, 1.6 SWR and 7.9 dBi bi-directional gain using the standard 1/2 wavelength feed-point elevation for modeling.

A cautionary note:  Modeling like this is to see what happens if...
In the real world, wire elevations, wire spacing, jumpers, sag and nearby objects mean some serious effort to tune this antenna.  Do not expect any directional pattern.  Under 1/4 wavelength elevation dipole radiation is circular and mostly up.


Title: RE: Anybody try this "Moregain" 80 & 160m antenna?
Post by: ZS5WC on March 31, 2016, 12:44:49 AM
 :)Hi Dick,
Thanks for your simulation-very interesting!..

I found this article-(In German) , that explains the relationship between the antenna elements , and also shows the SWR graph per band.
Looks like it is capable of good SWR, lowest point being 1.2:1 on both bands, which was quite impressive.

http://www.f4kip.com/wa_files/morgain.pdf

My German is not too good, but one can kind of follow what they are getting at.

Might try it when I get home-what is there to lose?.

73 de William
ZS4L / ZS5WC


Title: RE: Anybody try this "Moregain" 80 & 160m antenna?
Post by: ZS1KE on April 04, 2016, 07:41:29 AM
http://www.f4kip.com/wa_files/morgain.pdf

Hi William

Your article points straight back here

http://www.eham.net/ehamforum/smf/index.php/topic,61438.0.html

(link adapted for forum evolution)

I too am thinking I need to build one of these things.

Wouter ZS1KE


Title: RE: Anybody try this "Moregain" 80 & 160m antenna?
Post by: ZS5WC on April 04, 2016, 11:31:40 PM
 :)Interesting Thread there Wouter!..

Keen to try it myself with winter approaching..
Should be simple enough to build-the spreaders could easily be made from 20mm PVC conduit.

According to the article the SWR is good on both bands-who knows, you might get more harmonically related bands as a bonus..

Cheers,
William
ZS4L / ZS5WC


Title: RE: Anybody try this "Moregain" 80 & 160m antenna?
Post by: LA1BRA on April 07, 2016, 06:35:20 AM
I built one and used it for a week. Band width on 160 was about 30 khz. I think I made 1 local contact. Took in down because I had it installed below my 80 meter cage and the cage SWR went through the roof, too much interaction...Running a sweep with the VNA did not show very good SWR or resonance on 75/80, which could be explained away from it's proximity to the other antenna.

I built the spreaders with PVC as the other poster noted, simple enough to make these. Keeping tension and all that is a bit of a pain but doable.

I ended up building an inverted V, which does not have much broader bandwidth. coax feed, no balun, shunt against ground, it plays pretty good. I made the 40 foot vertical section like a cage dipole, then at the top, I ran a single wire out about 85 feet sloping to a post 10 feet off the ground.

K5VWZ  Tom
aka LA1BRA