Lets talk antenna for an 80

[Hulk]

He has a lot of the antenna above the truck. If I were you, I'd mount your ham antenna on the front fender. You can easily unscrew it and put a plastic cap (sealed with an inner o-ring) on the NMO mount when you're not using it. I keep both my CB antenna and my Ham antenna mounts capped until I need them, that way I'm not dealing with the antennas hitting the top of my garage.

 

[Hulk]

Here are some pictures of the mounts on my 80. Both of these are NMO mounts. I use one for my CB antenna and the other for my Ham antenna.

First, the front fender mount:

I usually keep it capped, unless I am on a road trip or 4WD trip. The caps are available at HRO or a CB shop, and have an o-ring on the inside to keep moisture away.

----

Here is the back mount on my 80. This keeps the majority of the antenna above the vehicle. I do have a shorty antenna that I could keep on here all the time (that would clear my garage), but most of the time I just keep it capped.

 

[Jacket]

Thanks Matt. I made the drive down to HRO on Saturday and talked to the guys behind the desk there, plus a couple of shoppers who just couldn't help themselves and jumped in to the conversation.

Not surprisingly, their recommendations were right in line with you guys. Roof top or trunk lid is best, but given the choice between hood mount and rear bumper mount, consensus was hood. So I came home with a lip mount similar to picture 1 above, a Larson NMO 2/70, and some cable. I installed it pretty high on the fender toward the cab, so it's mostly out of sight without being too close to the A-pillar.

They were out of stock on FT7800's, so I ordered one. Should be here by the end of the week, then the real fun starts.....

 

[corsair23]

General antenna question...not just for 80s anymore

I went ahead and bought a M285SNMO (Diamond 144-174MHz NMO mount antenna) to use on the 80 with the FT-8800. After spending a week on the road with Hulk for the Rubithon trip and experiencing the performance of his setup, I was pretty much convinced that having a 2m only antenna offered pretty good performance gains over the combo antennas. I still have my combo antenna should I need it but so far 100% of the time I've only been using 2m so this should work well.

My question is that the antenna comes with a cutting chart to "tune" the antenna. Length on the left if mm and Frequency along the bottom. Length goes from 1200mm down to 895mm to match up with the Frequency going from 144MHz up to 174MHz.

According to the specs the whip is 50" long to start and should be cut to length from there. The link above has the instructions but I am wondering how many people have, or would, even bother to do that? Or would you just mount it and run with it as is out of the package?

Based on the chart, my desired length would be anywhere from 47.25" (144MHz) down to about 45.25" (147MHz). 146.460MHz shows a length of just under 46" is optimal. I'm wondering if I should just trim the whip to 47.25" and call it good, or just leave it as is, or....

 

[corsair23]

Maybe that is why it was relatively cheap

So would I "dial it in" for something in the middle of my planned use (like 146.460) or for the lowest freq like (like 144.000) ?

 

[Bruce Miller]

Jeff, the first thing you have to do is find someone with an antenna analyzer and find out what frequency your antenna is resonant on right now. You have to do this before cutting (or adding) to the antenna's current length. I would shoot for a frequency that you usually use, say, the RS club's 146.46. When your antenna is resonant on 146.46, you should have a very low SWR on that frequency. Your SWR will climb as you change frequencies, up and down. Again, the antenna analyzer will tell you how far from your resonant frequency you may comfortably operate (before your SWR becomes unacceptably high). When you match your resonant frequency with the frequency you wish to operate on, your rig will be putting as much of its rated power into the antenna (transmitted signal) with little waste. (A high SWR can be damaging to your rig, too.) With an antenna that is matched to your desired frequency, your signal will get through where a poorly tuned antenna may not.

You know somebody with an antenna analyzer.

 

[Hulk]

I bought a shorter "garage friendly" version of the Larsen a few weeks ago, and tuned it to 146. I figured that I might as well optimize for our normal simplex freq., since that's what I use 90% of the time anyway. I used some diagonal cutting pliers to snip the whip.

 

[corsair23]

Jeff, the first thing you have to do is find someone with an antenna analyzer and find out what frequency your antenna is resonant on right now.

Thanks Bruce...Antenna analyzer = SWR meter? If so, I have a SWR meter which was what I was planning to use. If they are not one and the same then no I don't have one nor do I know anyone that does.

In other words, it should deviate to no more than 1.5:1 over a range of +/- 4MHz from the center frequency. So at 146.460, which is pretty close to the middle of where you'd be operating, you should expect around 1.3:1 as a max SWR at the corners if you're at 1.1:1 on 146.460.

Thanks Dave - My guess was to cut/tune for 146.460 and call it good but I like to hear my thinking is sound from a PE

I used some diagonal cutting pliers to snip the whip.

Thanks Matt...I was going to ask what I should use to cut the whip...I call those wire snips...Never knew they had a fancy name...So did you just cut yours based on length or did you "analyze" it first?

 

[Bruce Miller]

The two instruments are not the same. An antenna analyzer will connect to the PL-259 connector at the end of your coax. Like Dave said, the transceiver isn't used for this test. Using the antenna analyzer, you dial the meter to show a dip. This dip is your resonant frequency which is shown as a digital readout on the analyzer's meter. You can dial away from your resonant frequency, both higher and lower in frequency, to show the frequency range that you should feel comfortable operating in because the SWR is still at a reasonable level. If the dip matches a frequency far from your desired frequency, then it's time to "trim" the antenna, either by shortening it or lengthening it. I think that is a question on the ham exam, something about the relationship between shortening or lengthening the antenna to increase or decrease the frequency.

 

[Bruce Miller]

Jeff, I doubt you will have to adjust the length of your store bought antenna but going through the exercise with the antenna analyzer would make for an interesting project. A quick project, too, as it only takes a minute.

 

[corsair23]

Thanks guys - Interesting stuff

 

[rhyary]

I can't see this link. My user id is not authorized to see this one:
http://www.risingsun4x4club.org/foru...ghlight=setups

Can one of the moderators help?

Rami

 

[corsair23]

I can't see this link. My user id is not authorized to see this one:
http://www.risingsun4x4club.org/foru...ghlight=setups

Can one of the moderators help?

Rami

Rami,

That link takes folks to the Members Only section of the forum which unfortunately you don't have access to...You could join the club

I looked through the thread and there isn't much there that isn't here in this thread and other threads in the HAM section...I bet if you looked at Romer's ROTW posts on MUD you'd probably see most, if not all, of what is in the thread.

 

[rhyary]

Tnx, Jeff.
My 350R stopped transmitting. I can hear very well
When I do radio check with a local repeater, people on the net say that someone is trying to transmit but they can not tell who it is.

So my conclusion for now is that the antenna got whacked somehow. The mag comes with the think coax and it is possible the door got it kinked.

So I went a head the ordered the Diamond setup for the trunk gate.
It comes with the thin coax and it folds as well.
Here is my antenna order in case you guys see something fishy (I got the tri band antenna):
K400C - mounting setup with thin coax
CR-320A - triband 2m, 440, 220
SBB-1 - short dual band for our NE trees.

Rami
Counting the days to Moab 2011.

 

[wesintl]

me thinks its a setting on the 350. I have the same radio and I was able to talk to nathaniel on the CC on the way to moab but coming back I was having issues. I haven't looked into it much but I need to get it working. I think with mine though no one was saying they were hearing a transmit but no voice.

 

[corsair23]

Tone offset or whatever it is got changed? Sorry, still a HAM noob but I know when I first got my HT and started using it I spaced out the fact that although you can hear folks on the repeater, if you don't have the tone or what not set up right no one can hear you. Although maybe the fact that others were hearing the "break" means that this isn't the case.

 

[nakman]

Although maybe the fact that others were hearing the "break" means that this isn't the case.

 

[corsair23]

So I went a head the ordered the Diamond setup for the trunk gate.
It comes with the thin coax and it folds as well.
Here is my antenna order in case you guys see something fishy (I got the tri band antenna):
K400C - mounting setup with thin coax
CR-320A - triband 2m, 440, 220
SBB-1 - short dual band for our NE trees.

Ahhh...

You were probably looking for the parts "list". Here is the pertinent info from the thread:

FT-7800R -- Yaesu FT-7800R 2M/70CM Dual Band FM Transceiver. Wide Receive of 108-520MHz and 700-999MHz (Cell Blocked). NOAA Weather Alert. Illuminated keypad & microphone.
K400CNMO -- NMO Deluxe mount. w/6.5' RG-316 Teflon coax & PL259.
SBB-5NMO -- Comet 2M/70cm Mobile Antenna (Black), 3.0/5.5 Gain, 38" Length, NMO Connector

My setup is similar but the FT-8800, K400CNMO mount, and a Diamond antenna similar to the Comet (the Comet was on back order when I was buying).

I've been real happy with the mount aside from finding a reliable way to attach the thin coax to the upper gate to keep it in place and safe from getting pinched. The little doodads/clips that I've been using that have sticky tape fall off in short order when the tape gets hot, wet, etc.

 

[rhyary]

I switched the order to NMO type. Changed the short antenna to a diamond antenna to stay with one brand.

Most of the repeaters in my area are open. No need for tone. But the mic has an option (button) to change the tone, so I may have pressed something in inadvertently.

Damn, it was working so well when first installed. But anyway, the mag was only temp anyway.

The only think that could have change by mistake is pressing something on the mic. The 350R comes with multi function mic that has many buttons.

 

[rhyary]

Did system reset. Still no worky.
I really hope that the cable got pinched and somehow the new antenna will fix everything. If nothing else but to prove DaveInDenver wrong

But I talked to Yasue tech support and he sort of echoed Dave's opinion. The TX got toast somehow.

I don't have a good confirmation from the guys on the repeater but if they did hear something than that means I am transmitting but not very good. That may point out to the antenna.