The difference a doublet makes

[@jimricker403]

Thanks your videos for us FTDX 5000 owners are a great resource.

[@n4hnhradio]

Thanks Jim! There is so much to learn about the 5K. I’m more impressed every time I sit in front of it.

[@n4hnhradio]

Thank you so much, Jim! The 5K is a beast. There are many great radios on the market these days. I have observed that most hams aren't using their radios to their fullest potential. the operating manuals are sometimes unclear. I just thought I would share what I learned from the school of hard knocks, in case it helps others.

[@ScottBrown1406_Repair]

Never can have too many Antennas!

[@n4hnhradio]

Amen to that!

[@artc9114]

Just for some quick advice. Remember the doublet antenna system is as only as good as the Antenna Tuner. A true doublet does not use any coax. The type of tuners recommended for this is preferably mechanical style with a T or L network with a tuning start point capability of 10:1 ... Terminating to the back of the tuner using the 4:1 balun built in most of the older Tuners. But now there's a consensus using a 1:1 current balun like the new Palstar AT5K tuner has the 1:1 built-in ... If the tuner does not have a balun built in the T or L style network tuner will work fine on the output side with a short coax jumper to the external balun of choice.

[@n4hnhradio]

My Palstar AT-Auto failed. It has a 4:1 BalUn. I switched to using the internal ATU in my Elecraft KPA-1500, using an external 4:1 . I haven’t looked back. I haven’t even cared to fix the Palstar. But, before I went back to a 4:1 BalUn, I experimented with a 1:1. It didn’t allow me to cover as many bands with a suitable SWR. I showed my experiment with a crazy 1:1 97-Ohm BalUn that Balun Designs recommended for a Doublet. It was not good. I should have returned it. It was a waste of money. Here is a link: kzbin.info/www/bejne/paa1o6pjh8tjl5Isi=9z23FZDOD0agUsRH I went back to the reliable 4:1. It is working incredibly well. Here is the video: kzbin.info/www/bejne/joq8aKN_aNymprMsi=ssWFDVdCytqLrX4A

[@reallybadaim118]

Excellent antenna indeed.

[@awksedgreep]

I’m sold. Need a full legal limit replacement for my efhw and need to move my ham shack toward the center of my house. Reducing noise and longer feed line are big benefits as well.

[@n4hnhradio]

You might find these videos interesting as well. Watch them in order. kzbin.info/www/bejne/paa1o6pjh8tjl5I kzbin.info/www/bejne/joq8aKN_aNymprM

[@abrahamnorthhampton3327]

Fine business. 73

[@jdotson41041]

What type of lightning protection do you have for your 450 ohm feed line?

[@n4hnhradio]

The feedline comes to a Balun. I covered that extensively in videos last year, around the Spring time. Those videos are still visible. They haven’t been moved to Patreon. From the Balun to the amplifier/ATU is a 9 ft. run of LMR400. All of my other antennas go to an Alpha-Delta antenna switch. I always leave the switch in the grounded position when I leave the shack. There is an open position on the switch. I unscrew the LMR400 from the back of the amplifier/ATU and connect it to the open position on the antenna switch when lighting approaches. I unplug the power to the radios. The power company will tell you that the only truly reliable protection from lightning is to unplug. I have used the aforementioned technique since 1998 at this location and I’ve experienced no lightening damage. My power company told me that my zip code gets the most lightening of the entire metro area. So, anecdotally, it seems that my method is working.

[@n4hnhradio]

Back when that video was made, I used a Palstar AT-Auto. It has a built-in Balun so the ladder line came into the shack to the back of the tuner. That tuner failed last year so I started using the auto-tuner that is built into my Elecraft KPA-1500. But it has no connection for ladder line. I installed a 4:1 Balun just inside the window. The ladder line comes to it. 9 feet of LMR400 goes to the back of the Elecraft KPA-1500.

[@azcharlie2009]

My understanding is that ladder line will not radiate. Is that true? Or, do you get some RF in the shack?

[@n4hnhradio]

That’s correct, in a perfect installation. My ladder-line runs near a downspout, which is unavoidable. My ladder-line is also near one of the lengths that falls into resonance (approx 57-60 feet). 65 feet is a point of resonance. It can actually act as an antenna, receiving RF radiation from the antenna and feeding it back into to the shack as common-mode current. But ideal lengths, like 40 or 80 feet, weren’t practical in my installation. The center of the antenna is at 45 feet. Coming straight down and into the shack, via the window, and then over to the back of the tuner, took another 12-15 feet. The bands that seem to produce the most common-mode current in my scenario are 15, 30, and 40 meters. For the other bands, I’ve been able to choke the RF by placing ferrite chokes on wiring such as the mouse, the monitor, the mic cable, and the cable between the computer and the radio’s CAT port. I was going to experiment with adding some ladder line to get it closer to 80 feet but 1> I would have to find a place for so much additional line to be routed and 2> the antenna is below a 2:1 SWR across 17 and 20 meters without the tuner, though I sometimes allow the tuner to touch up the SWR a bit. It performs very well on 17 and 20 meters. So, given the performance of this doublet as-is, I just figured I would leave well enough alone. 73, de N4HNH

[@izzzzzz6]

@@n4hnhradio Avoid 64ft of open wire ladder line at 40M. 42ft-52ft or 73ft-83ft of line is best (+-10ft), at least for 40M around those lengths.

[@n4hnhradio]

Yes. I’ve seen the charts on that. Mine is in the 50 to 60 foot range, maybe 55. I don’t use mine for 40 normally but it works great at night on 40 for DX. During the day, my ZS6BKW beats the doublet.

[@rickmckee6698]

Man, you need to turn the radio down some and speak up into the mic so we can hear what you are saying. Kind of hard for the ears to compete between hearing you and null out the radio at the same time.