M104C converted to 10

[wavrider]

Marconi,

Yep you are right with that spacing.

I played with so many yagi's over the past three decades and always came back to that wl spacing as it was the best I could find.

I did build some five and six element yagis.

The basic was always .15 wl from reflector to driven, then .125 from driven to first director, then .15wl from first director to second, for both the five and six element I went .25 to third and fourth director also I reduced each director by 5% accordingly.

It was a darn rifle shot for a front lobe on that six element.

 

[wavrider]

how did the yagi turn out?

 

[airplane1]

Wow you guys are great. This is the best info I got so far and explained so well, better than the internet lol. That is one of the reasons I like this forum so.

I can not wait to get going on this. I will post pics as I progress. I am putting one more section of tower up to raise the top of tower to 40ft. and I am in the process of welding up a bearing plate to accept a 2 in. bearing and the beam will be flatside about 2ft above the bearing with an Imax or A99 a few inches above that.

I took my maco 5/8 down and was pleased to see it was in very good condition for being up since 2003. I will only have to replace some of the screws as they are rusting. I will store if for the future if needed.

I have a Alliance HD73 rotor that is going to Norm's rotor service for a look over and then hopefully it will handle the antennas I am putting up. It is the best I have for now.

Thanks for the awsome info,
AP

 

[davegrantsr]

I took my maco 5/8 down and was pleased to see it was in very good condition for being up since 2003. I will only have to replace some of the screws as they are rusting. I will store if for the future if needed.
AP

try putting the maco back up just above the yagi without adding the radials to the v5/8. the yagi will act as the groundplane. i'd like to think performance should be better then that of an antron.

 

[airplane1]

By the way, Should I just mount the beam shooting straight up so I for the tune process?

Do you think the maco 5/8 will work without the radials and mounted above the beam?

Thanks,
AP

 

[Marconi]

By the way, Should I just mount the beam shooting straight up so I for the tune process?

Do you think the maco 5/8 will work without the radials and mounted above the beam?

Thanks,
AP

Airplane1, I re-read this thread and I noticed that you have a M104c that you indicate has a 26' foot boom. My M104c is only 17' feet. That may be a bit too long for 10 meters, but you'll have a lot to play with if you really have a 26' footer. Are you sure you don't have a M105c?

I hope you have lots of energy to try and convert this antenna to 10 meters. If I'm right, and this is your first beam then you'll have your hands full. I would also say, if you do have the energy---then try anything that suits your fancy and try davegrantsr's idea with the V58 even though I have some doubts that the beam will make a good ground plane. If you have an A99, you could try out both above the beam during the tuning process on the beam. I have a feeling however, that no matter what you do with the beam close to Earth during the tuning, when you raise it up to installed height you may well see things change.

I've put a Starduster, with its slanted down radials on a 10' mast, above my 4 element beam before. In that case the radials were within about 2' feet of the beam, and I didn't notice any ill-affects on either antenna, but that was a long time ago, back in the 80's and I think I know a little better now what to watch for. I never thought about using the 1/4 wave radiator without the ground plane however, but if you think the V58 will work with such a setup, go-for-it.

At some point in time, and for a minute or two I considered the idea of pointing the beam straight up while tuning. But, I could never figure out why? It just didn't seem like a good idea to me, unless I could get the beam away from everything that was likely to be affecting the tune---and that just didn't get me far enough away from the Earth.

Just plan on some repeated steps in the tuning process, and the farther away from a known working setup design you try the more experimenting you'll likely have to do.

Keep us posted and be careful if you have power lines anywhere near your working site.

 

[airplane1]

Marconi, I do have the Maco 4 and it does have a 16ft boom not the 26 as I stated early in my post. I did correct that type error in a few posts down from when I first posted it. Someone else caught it Ha Ha Ha.

Anyway, I am going to do what Waverider say and use the formula posted and set the 4 elem beam up for 28.400 and mount it up about 10ft flat for tuning and then if all goes as planned with out getting upset and smashing it I will put it up 40-45ft with A-99 above it. I would try the maco above it but I dont have the energy to do all that experamenting at this time LOL.

AP

 

[wavrider]

Airplane1

Maybe set the beam at 6 feet in the air if you can, makes it easier to adjust the gamma without having to use a ladder.

Marconi or anyone help me out here as I am going by memory but when the yagi is raised in the air I think it will raise the resonant freq about 100 to 125kc's compared to it being near the ground. I may be wrong but I think that is the rule of thumb.

If my memory is correct you will want to set the vswr at 28.3 at 6 feet off the ground and it should rise to 28.4 once in the air.

I would have to read my Mosleyproth67b manual to refresh my memory as it is stated in there how it works.

Adjusting the gamma can be fun, I have always adjusted the gamma rod (cap) for lowest vswr then moved the shorting connector in or out until I got the vswr curve I was targeting.

You will want the vswr to be minimum at your target freq and rise evenly on both sides

Example is 28.3mhz target assuming a 1mhz spread high end will be 28.8mhz low end will be 27.8mhz.

This way with the measurements given it should be optimal performance at 28.4 once raised in the air. If my memory serves me correctly on how the vswr vs height above ground works.

Do not be surprised if you have a broad bandwidth using those element spacings, you will probably get into 29mhz before you see 2.1:1 vswr and way down into 27mhz before you see 2.1:1 vswr.

Take your time adjusting that gamma, play with it and learn how the relationship between the gamma rod and the shorting strip to the driven element will effect the vswr of that yagi.

If you have an analyzer it makes it so much easier to adjust it.

Also use the same length of coax you will use once it is installed when you are setting the vswr, lay it on the ground and not rolled up.

Some say the length of coax does not matter, I will not take any part in that argument. I will just say it is easier to adjust the gamma with the same length of coax on the ground, than to find out that the vswr changed drastically once you went from a 10 foot jumper to 60 feet of coax. Sort of hard to adjust that gamma 45 feet in the air.

Experiment, adjust it with the length of coax you will use when it is on the tower, then connect a short jumper to the yagi and check the vswr again to see if they have changed just by changing the length of the coax.

Theory says it should not change, theory also says a honeybee can not fly.

Use some coax seal or at least some good black tape on the coax connection once it is ready to go up in the air, do not need any water intrusion at the connection.

You can also put good black tape around the gamma rod connection where it slides in and out to keep the water out once it is adjusted, stops the gamma from getting iced up in the winter if you are in one of those areas that have freezing weather.

Friend called me up and was telling me how he was working New Zealand and England at the same time on 27.555 at 10 am Local time East coast. He said the band was open for over three hours so the openings are starting to happen. Get that yagi in the air and get you some contacts.

I had to reply that I was working JA's and JO's on 15 meters at 5pm local time here also.

 

[airplane1]

Thanks again waverider, You and marconi have been a welth of great info for me. I am starting this project this weekend. Been looking for some 2 inch muffler clamps with a good rust protecting coating or stainless, stainless are just to expensive. This is going to be a cool project and I am excited to see what happens. If this beam is broad banded it will be a big + for me as I would like to use it on 11 also but 10 being my priority that is where I will tune it, got a AT1000 tuner for 11.

I have an MFJ259 so it will be nice to not be running in and out of the shack. I bought it hoping to do antenna projects some day and now I get to use it and hope to many many times more.

73,
AP

 

[wavrider]

You will enjoy that analyzer, I use mine often and it makes antenna building so much easier.

Post the info of how the yagi turns out and most of all have fun.

The experience you gain from this project will help in future antenna projects.

The 5/8 will do you justice on top of that four element, more so than the
A-99, use the A-99 for a fishing pole and use that 5/8 for vertical on the tower.

It is worth the extra effort required to experiment with that 5/8 on top of the beam instead of the A-99.

The 5/8 will give you roughly 1 to 1.5 DBD gain and the A-99 well lets just say it is less gain than a dipole.

If you have a better antenna why not use the best you have? The 5/8 is more superior than the A-99.

 

[airplane1]

I figured out how to run my download of quick yagi, I am enjoying playing with it. You can real play around with all aspects of a yagi and check patterns,swr,ohms on graphs or plots with front to back db + gain figures. I got a yagi to do 10db gain but it only had 18 db f/b using a 16ft boom.

I put in the info I was given here and it was very good. there is a optimize button too.

I will get the beam built as soon as I quit playing around LOL.

AP

 

[wavrider]

I figured out how to run my download of quick yagi, I am enjoying playing with it. You can real play around with all aspects of a yagi and check patterns,swr,ohms on graphs or plots with front to back db + gain figures. I got a yagi to do 10db gain but it only had 18 db f/b using a 16ft boom.

I put in the info I was given here and it was very good. there is a optimize button too.

I will get the beam built as soon as I quit playing around LOL.

AP

Glad to hear you got the program running, have fun playing with the yagi.