Discussion in 'Antennas, Feedlines, Towers & Rotors' started by NN2X, Dec 6, 2019.
I have measured the looking into the 1/2 wave on 40 wire two ways (fed about 1 ft above the ground and the wire running straight up at about 45 deg WRT to the ground) and I get good agreement. The Z is about 3700 ohms shunted by about 8.5 pF at 7 MHz. It turns out that the FT-240-43-based 1:49 behaves somewhat like a conjugate match to this Z.
I now use a Fair-Rite Products 2643251002 core with the same winding config but its input and output Z's are a bit different. This resulted in a min SWR to be lower in freq but shortened the wire up from 67 to 65 ft. Also I have to compensate for residual reactance looking into the transformer a little differently. Instead of a simple shunt 100 to 150 pF, I added a series inductance of about 0.28 uH and then a shunt C of about 180 pF across the input. This is with a 2.4 k resistor simulating the ideal load of 49 x 50. If it wasn't 11 degrees outside I'd put this latest config out in the electrical box to test it. Presently I just have a 100 pF shunt C across the input as a first try. I am anxious to see if the wire can be lengthened back to 67 ft.
This transformer also has a lower loss at 7 MHz with just the shunt C. Later tonight I'll test the transformer loss with this series L/shunt C. Fun tinkering with this stuff.
I just confirmed with the designer these monoband EndFedz designs use an L network approach to establish the impedance conversion. Hence I was wrong for assuming a transformer ratio of any kind as there is no transformer per se. The potential bonus is more efficiency plus higher power limit at the cost of multi band operation. Viva la choice.
I'm ordering an EF-30 to add to the next round of EFHW H-Field tests. I will also add a far-field monitoring capability to address Rege's legitimate "antenna measuring contest" request so readers have lots of data to chew on to make up their own mind.
I'd say proceed with your vertical deployment keeping the feed box off the ground as you propose and others here suggest with the cautions as expressed.
I am the original Ham for this thread...NN2X
I am extremely please of the results..Actually, if there is a problem, my TX maybe be exceeding my RX..(Slightly)...But with my 100 Watts, works great...I can't complain..I worked about 10 stations, from California to Florida, and north east...
To refresh, I used PAR End fed antenna for 20 meters Mono bander 1/2 wave dipole, but fed at the bottom, and antenna is vertical (33FT in Height)...using telescopic antenna (Paint Pole / and dowel (Balsa) for the last 10ft ...All from Home depot...Cost about $35
Really pleased...No ground radials, no fancy transformer, other than using the PAR antenna 1/2 dipole, with 9:1 transformer...
Now, moving to the goal, get the digital modes working, and start transmitting CW...
And get my son, involved! (KI5FJE)
Thanks all of you for your support...
Let me know when you can get on CW and we can make a "sked" for a contact. I'm in and out all day today but should have some operating time here and there and 20m will work for this path during a lot of the day...towards the end when the sun is setting propagation changes a lot and I wouldn't hold much hope after that.
If you can "work" more than you can "hear," you don't need an amplifier! The handicap there is likely to be man-made RFI and whatever part of that is generated in your own home could be a fun fishing expedition to find the sources and reduce them one by one. Your son can help you with that, as turning stuff on and off while listening to a receiver goes faster with two people.
The "box" on the PAR is either a L-network, or a 1:49 transformer? Tom, can u check which it is?
Welcome back. Even with a marginal tuner, I wouldn't expect much trouble with 20m on just about anything.
If all else fails - consider the "Amazing 20m Coil-Shortened Shower Rod Dipole". The original was like SWR 1.3 right off the bench.
Good luck, and keep us posted!
Jim, WQ2H / WK2XAH
I already checked with Dale. It should be an L network for the monoband LNR/Par antennas.
Just skimmed thru all the posts and didn't see anyone Mention that a 5/8 wave had a better gain than a halfwave , Just happens that a popular number of 43 ft vertical antennas are a 5/8 wave at 14 MHz !.
Make your vertical 43 ft and take advantage of the extra gain.
WB2WIK...Steven! Sounds great, I surely don't need no amp..I just had another 5 or 6 QSO, all the same response...My TX slightly stronger than my RX..., not by much...The Hams I had QSO with this morning, had dipoles, yagis and verticals...So...For now this is not bad..
About CW....Sked...I wish! I sold everything..so, I don't have a Key...Can you imagine...
But give me until next week, and I will get a straight key.
If you wish, we can use SSB...sked..