Off air on 75

[w1vtp]

Blew the 75 meter traps.  40 still works

Al

[Opcom]

Too much power or water and weather? I thought traps seldom fail, last decades.

[Steve - K4HX]

Why use traps in the first place? If 40 and 80 is all you want/need, a fan dipole will work FB with no power or moisture related crap outs.

[AJ1G]

If you don't have replacement traps, can you easily lower the antenna and at least for now replace the traps with insulators and then use removable jumpers to shift from band to band?  Not automatic, but at least you will be back OTA.  I don't have traps, but I use links on the end of  my 75 meter inverted vee to add about 3 feet to each side  to resonate it down on the CW end of the band.  I can drop the ends of the antenna to connect and disconnect the extensions.  I am currently using small electrical panel ground /neutral bar connectors as the link connectors.  They are small aluminum bar stock drilled with 5 holes and set screws, just connect a jumper from the extension pieces to the main legs. Stocked in the electrical connecter section at the Depot near the wire nuts and lugs.

[W2VW]

Too much power or water and weather? I thought traps seldom fail, last decades.

The gurus who repeat that a lot seem to have some $ interest in traps.

Ain't a trap in North America can bother me.

[Opcom]

Too much power or water and weather? I thought traps seldom fail, last decades.

The gurus who repeat that a lot seem to have some $ interest in traps.

Ain't a trap in North America can bother me.

I have no traps and do not want any. I see them as a compromise that brings benefits along with a reliability risk, but I thought the risk was small.

[Steve - K4HX]

It's not that traps are inherently bad. But they are another component in the system that can fail. They are another component in the system with a certain amount of loss (it can be very low if properly designed and built but the trade offs are further complication, cost and weight). If you want multiple bands with one wire, traps can make that possible. In this case, for just two bands (80 and 40 meters), I see traps as an unnecessary complication given that a fan dipole is easily created.

Too much power or water and weather? I thought traps seldom fail, last decades.

The gurus who repeat that a lot seem to have some $ interest in traps.

Ain't a trap in North America can bother me.

I have no traps and do not want any. I see them as a compromise that brings benefits along with a reliability risk, but I thought the risk was small.

[W3GMS]

Al,
Why use traps?  Bandwidth of antenna is reduced and its just another place to add loss.  I think you have the real estate to put up a full size antenna.  Go with open wire line and tune it if you want multi band operation. 

If that won't work for you, then Steve's suggestion of a multi-band dipole is a good way to go if coax is your thing.

Joe, GMS 

[W2VW]

Traps have an impossible job on the higher band when operating out of resonance QRO. Move 75 kc and see stuff dripping out of the sky onto your new BMW's hood.

That alone is enough to look elsewhere for another way to make the skyhook take energy.

Then there's weight, ugliness and weather.

[K6JEK]

I ran an 80/40 W9INN for years. He didn't call them traps. He called them resonactors. Nice word, don't you think? It fit the space perfectly. When I switched to full length antennas, no one could tell the difference. Admittedly I didn't do A/B tests but at the time I was in daily, lengthy QSOs with people all over the state. These guys noticed everything and did not notice an iota of change.

[Steve - K4HX]

Used the set up below for 3-4 years. Wire was insulated #12 stranded (Home Depot/Lowes stuff). Height was about 70 feet. All FB.

[W3GMS]

I ran an 80/40 W9INN for years. He didn't call them traps. He called them resonactors. Nice word, don't you think? It fit the space perfectly. When I switched to full length antennas, no one could tell the difference. Admittedly I didn't do A/B tests but at the time I was in daily, lengthy QSOs with people all over the state. These guys noticed everything and did not notice an iota of change.

Hi Jon,
I do believe if you ran an A/B test and all other things being equal which is sometimes hard to do that the full size antenna would definitely have an advantage.  Just do an engineering loss comparison on the two designs.  Its just like guys with G5RV saying they work as well as full size antennas on the lowest frequency of operation.  Plot an SWR curve on a trap antenna and you will see that the bandwidth is narrower.  Then some ops use and antenna tuner and think that helps the radiation efficiency model !!   

I have nothing against traps or G5RV and I realize that some folks have little choice so they use them.  

Joe, GMS    

[W3GMS]

Used the set up below for 3-4 years. Wire was insulated #12 stranded (Home Depot/Lowes stuff). Height was about 70 feet. All FB.

I have used a similar antenna years ago and it worked very well.  If I ever get sick of my open wire line that is what I would switch back to. 

Joe, GMS

[Steve - K4HX]

I later put up a reflector for 40 meters to create a 2 element Yagi pointed west. Ran out of time to put up a reflector for 80. It probably would not have worked all that well anyway, given the height.

[steve_qix]

I also use the fan dipole method here for 160 and 75 meters.  The only difference is that the antennas are at 90 degree angles to each other.

I'm going to try the arrangement Steve HX uses when I return to Rattlesnake Island after ice out.  I need to be able to get on 160 meters from up there.  Open wire line is not an option at the Island.

[Steve - K4HX]

If I had to do it again, I'd use wider spacing - more like 4-6 inches or make the 40 meter legs very taut. The wind once flipped the 40 meter leg around and the two wires made contact. There was some zorching and arcing. It burned through the insulation and also crapped out the SO-239.

[W1ATR]

Used the set up below for 3-4 years. Wire was insulated #12 stranded (Home Depot/Lowes stuff). Height was about 70 feet. All FB.

Steve. Does the length of the spreaders matter? Have lots of 4 and 6" plastic ones hanging around.

[W1ATR]

OK, nm. I didnt see that last post from you a few minutes ago. 

[Steve - K4HX]

No problem. I was in the middle of answering anyway. 

It matters but not very much.  It just means whatever amount of interaction there is between 80 meter dipole and the 40 meter dipole is different. Either way, you will likely need to trim one or both of the dipoles, so it's really irrelevant. You can use the speaders you have and like I said previously, I recommmend a wider spacing.

[W2VW]

No problem. I was in the middle of answering anyway. 

It matters but not very much.  It just means whatever amount of interaction there is between 80 meter dipole and the 40 meter dipole is different. Either way, you will likely need to trim one or both of the dipoles, so it's really irrelevant. You can use the speaders you have and like I said previously, I recommmend a wider spacing.

I haven't had to trim a wire antenna in years.

[Steve - K4HX]

Not physically.

[KM1H]

Ive run 160/80 common feed dipoles for decades and the current config is 160/80/75 so rigs/amps that cant handle the VSWR work well. I dont bother with tuners or open wire, coax is all I'll use.

The 80/75 are seperated by about 30 degrees and a bit off 90 degrees from the 160 because of limited tie off points in the woods unless I want to do a lot of clear cutting. A little wire trimming brought everything where I wanted.

At 180' apex its a bit too high for photos. Many times Timmy tells me Im the only station he can copy 100% when on his mobile runs and thats just with various exciters.

With the 40M yagis down for changes Ive added a 40M inverted vee at right angles to the center of a 80M sloper which starts at 100' on another tower. That
required no tweaking.

[w1vtp]

The fan dipole is certainly an attractive option.  The reason I stayed with the trap approach is that after almost 30 years of flawless performance, I retired my trap 80 / 40 meter dipole only because the wire at the center of the dipole was about to part way.  Adding 160 meters was a natural progression for the time being.  Unfortunately, I'm quite sure I zorched the 75 meter trap.

I will discuss the fan option with my friend Bob, KB1QV who is my antenna monkey.  He is the one who climbs up and down my tower, house roof etc.  The trap dipole was premade and ready to put in place.  I should have figured out that something was fishy because I had an unusual crap out of the SDR program two successive nights before the big crap out of the antenna.  I think I was arcing over on one of the traps and that was what was the culprit for the program hangup.  The plan is to lower the antenna just enough to replace 75 meter traps with insulators and will just have to be off for the winter on 160 (sigh).  I will probably have to readjust the length of the 75 meter portion with the removal of the 75 meter traps.

Even though I have dropped my power by more than 10 dB and am operating into a really screwed up VSWR I still get out pretty good but I really need to not stress the automatic tuner in the Flex.

I'm pretty sure that Joe WA2PJP is using a fan dipole and he is quite happy with it so between Steve's and Joe's and others on this thread recommendation, I will certainly discuss this option with Bob.

I'm still pretty good on 40 meters so I may see you all on heavy iron night on 40 - the freq is 7160, right?

73, es Happy New Year all

PS:  I can't say enough by way of appreciation for the help that Bob has given me in the past few years with my antenna.  He is also the one who kept badgering me about tearing down the old garage and putting up the new shack.  Without his encouragement, I would have a silent key before my time

[WU2D]

Gee I am sorry I burned out your antennna Al.

Mike

[W1TAV]

Mike, I am not sure if it was you or me..   Al, I drove past your QTH on my way down Sinclair Ave. to the cell site Friday morning.. Maybe my 12 watts of AM  was too much for your system..