Truck bed beam

[M0GVZ]

Why would that mean no ground plane? If I have my riser grounded to my chassis what does it matter?

The ground plane starts where the coax braid ends, not two or three feet away. Its all about the amount of metal DIRECTLY UNDER THE ANTENNA STARTING WHERE THE BRAID ENDS and you have none, well to the antenna you have a circle or square the horizontal area of the riser. Sure it may meter real well with your ohm meter but that's DC and RF is AC and to get a true indication of impedance it needs to be measured at the frequency its being used on. The only thing using an Ohm meter achieves when it comes to antennas is to tell you there's a connection. They cannot tell you how good that is for RF in any way, shape or form. They are in effect about as much use as a chocolate fireguard. They will for example show a dead short on an antenna socket with an antenna that is DC grounded yet to RF that dead short is invisible and doesn't exist.

If you think it works great then stick a 1/4 wave whip on the mount, get an antenna analyser and measure what the value of the impedance is at resonance. Anything other than 36.8 Ohms means there are losses.

And for the second time im not cophasing the two antennas. There's only gonna be one hot antenna in this setup with the second in the rear to block the backdoor so I dont need 9 ft.....I only need between 6 and 7.

The one not being used will be parasitic. A lot of the current flowing out of the hot antenna will end up flowing in the one not being used.

On a 4 square array antennas are spaced 1/4 wavelength apart to give the best gain AND DIRECTIVITY. No point having tons of gain if its not going where you want.

Ultimately given how much better a properly installed antenna would work compared to both the piss poor install you have and the even poorer one you're planning, putting two antennas on would be both a waste of time and money.

 

[726roN]

The ground plane starts where the coax braid ends, not two or three feet away. Its all about the amount of metal DIRECTLY UNDER THE ANTENNA STARTING WHERE THE BRAID ENDS and you have none, well to the antenna you have a circle or square the horizontal area of the riser. Sure it may meter real well with your ohm meter but that's DC and RF is AC and to get a true indication of impedance it needs to be measured at the frequency its being used on. The only thing using an Ohm meter achieves when it comes to antennas is to tell you there's a connection. They cannot tell you how good that is for RF in any way, shape or form. They are in effect about as much use as a chocolate fireguard. They will for example show a dead short on an antenna socket with an antenna that is DC grounded yet to RF that dead short is invisible and doesn't exist.

If you think it works great then stick a 1/4 wave whip on the mount, get an antenna analyser and measure what the value of the impedance is at resonance. Anything other than 36.8 Ohms means there are losses.



The one not being used will be parasitic. A lot of the current flowing out of the hot antenna will end up flowing in the one not being used.

On a 4 square array antennas are spaced 1/4 wavelength apart to give the best gain AND DIRECTIVITY. No point having tons of gain if its not going where you want.

Ultimately given how much better a properly installed antenna would work compared to both the piss poor install you have and the even poorer one you're planning, putting two antennas on would be both a waste of time and money.

All you have to do is run some grounding wire to the chassis. Now the whole chassis is ground.

 

[726roN]

All you have to do is run some grounding wire to the chassis. Now the whole chassis is ground.

This is the update on the truck bed beam. The rail closest to the cab is permanent for when I go mobile (switched to the MM9 monkeymade). The back rail and the boom are removable and easy setup. RG-213 coax with ground wire to chassis. Low Swr 1.2:1 all channels.

Will update I get the beam tuned up.

 

[psycho]

As close as the hot and reflector are together, it will never work.

 

[psycho]

2 antenna setup is a cophase setup I think you want to run a dual hot setup and they need be a min of 48" apart 60" would work much better

LMAO!

 

[726roN]

As close as the hot and reflector are together, it will never work.

Why would it never work if I already have it working as we speak. I haven't even given you the measurements so how do you know if it's too close or not?

 

[psycho]

Why would it never work if I already have it working as we speak. I haven't even given you the measurements so how do you know if it's too close or not?

7-8 ft apart is the sweet spot and given the tiny length box of the Frontier crew cab, you are a bit short. Just because it matches in OK doesn't mean it'll gain anything.

 

[222DBFL]

And no metal under the antennas. How's it's supposed to tune correctly?? Use 2 firesticks I suppose. Waste of time. Should just place one good antenna on roof and be done. Get a good mount and antenna and you won't need 2 antennas for that little truck. Also again looking at the photos you can't just add a ground to the frame you have built from the truck frame and think it's going to work. You need metal directly under the antenna. And I'm not talking a couple inches. Look at a real 2 antenna comp setup and you'll see they use suburbans and such as they have a large metal roof. Get a 3" Breedlove single hole mount and a sirio 5000 performer and quit wasting your time with the 2 antenna setup. JMHO.

 

[wavrider]

65" of separation between driven element and reflector will work just fine. That is roughly .15 wl spacing, max gain is at .25 wl spacing but is not much more gain than .15 wl spacing.

Look at JO GUNN beams spacing, nothing is optimal on them yet they work, just not as well as JO Gunn's advertising states.

Build your beam test it make contacts and have fun.

 

[726roN]

7-8 ft apart is the sweet spot and given the tiny length box of the Frontier crew cab, you are a bit short. Just because it matches in OK doesn't mean it'll gain anything.

The measurement between the two antenna are 72"

 

[222DBFL]

6ft should work. Should work I say. You may have to play with distance back and forth on the reflector antenna. The front one will be your hot and the rear the reflector. Are you still planning on using the 4ft firesticks?? Just curious. With going through all the trouble you've went through I do hope it works for you. But like I said from the first post, a single antenna as close to 108" total length physically or as close as possible to that length will work best on the roof of the truck about 8-10" forward of the rear of the roof. But you already have your mind set, so again I wish you good luck and enjoy experimenting.

 

[wavrider]

i have never experimented with any type of mobile beam set up.

I have seen some on you tube videos at mobile shoot outs, found them interesting as to how you can get any direction and gain out of a yagi that is only a few feet of the ground, would seem to me that it would be a great big omni radiator, but i guess some how they manage.

For shooting skip, I would find a push up pole, an Imax2k, and get on top of a mountain with that push up pole about 36 feet in the air with the I2K connected to your mobile and then make some contacts

 

[DJboutit]

If you really want a competition setup just get 2 MR Coily enforcer comps I have run 2 before hey work really good

 

[M0GVZ]

All you have to do is run some grounding wire to the chassis. Now the whole chassis is ground.

...for DC. RF is not DC.

You're trying to make the body of the vehicle appear as one massive sheet of metal so the RF flows over it and not the lossy ground.

 

[AudioShockwav]

All you have to do is run some grounding wire to the chassis. Now the whole chassis is ground.

And I will echo what M0 said, you have a DC ground, not a good RF ground, they are two different things entirely.
You can run a 16 gauge piece of wire from your mount to the frame and show low ohms to the rest of the truck at DC but RF will not see it that way.

appear as one massive sheet of metal so the RF flows over it and not the lossy ground.

This is true shizzle, you can take a field strength meter and see that you are getting "some" gain out the front, but not like you would if you properly mounted the antennas over a nice solid sheet of metal.
Even the guys on the other forum you have been asking the same question too have been telling you the same thing.
If Peek-A-Boo is giving you advice about your antenna set up it would be in your best interest to listen to him..... He has played this game before.
You do not get trophies at shootouts running lossy antenna set-ups.
The suggestion he gave you about mounting a camper shell and lining the inside with metal is a damn good one.
I have some pictures somewhere of a little pickup with a camper shell that is lined with copper mesh and bonded to the bed and frame.
It was a kick ass set-up......And I do mean kick ass.

73
Jeff