rover67
Rising Sun Member
Nice, glad you could use them!!!!
Confession?
- Thread starter rover67
- Start date
rover67
Rising Sun Member
Well that was dumb....
Read somewhere to stagger tall springs in the 80 (B left front, B right rear) so I did that an the right side if the truck is taller than the left, so I'll be sticking the B in the left rear like I was supposed to to begin with.
Read somewhere to stagger tall springs in the 80 (B left front, B right rear) so I did that an the right side if the truck is taller than the left, so I'll be sticking the B in the left rear like I was supposed to to begin with.
DaveInDenver
Rising Sun Ham Guru
What do they recommend with 60s? Might be a leaf spring vs coil thing? I understood the reasoning for the cross height was to compensate for torque during acceleration. On leafs the springs are rated (+) (0) (-) based on actual arch or something like that but maybe they get less variation part-to-part with coils?
rover67
Rising Sun Member
I think on the coils, at least what I can gather, they used to do DS and PS, then they switched to A and B. As with the leaf springs (+, 0, - last time I did them), what I typically do is set them on the floor and figure which is taller and use that on the Drivers side. I second guessed myself here because some thread on 'mud (go figure) said some stupid crap about putting the taller spring on the pass side rear of the 80. AND when I measured ride heights before doing the rear and after doing the front it looked like the taller spring might actually need to go in the right rear.. anyhow once it came up level, it changed and the right side is higher by a half inch front and rear..... Sooooooo hence the need to swap..
Edit #1, On the 60 they said taller on left (US DS) with the springs being taller to shorter from +, to 0, to -
edit #2, the coils were like different by 1/4" free height... so not a small amount. seems intentional..
Edit #1, On the 60 they said taller on left (US DS) with the springs being taller to shorter from +, to 0, to -
edit #2, the coils were like different by 1/4" free height... so not a small amount. seems intentional..
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rover67
Rising Sun Member
Tonight’s hour in the garage included some radness such as swapping springs in the rear and replacing exhaust hangers. Lesson I’ll never lear DON’T OVERTIGHTEN SHIT!
broke a stud off one of the new hangers. Luckily I had an extra. Bought three only two were broken.
Maybe this will get rid of my clunk in the back....
broke a stud off one of the new hangers. Luckily I had an extra. Bought three only two were broken.
Maybe this will get rid of my clunk in the back....
rover67
Rising Sun Member
I also forgot to mention I got the Gamiviti Awning mounted with the Gamiviti brackets to the stock roof rack. I’m pretty stoked about this since I just wanted the awning and no big roof rack for now. Super clean and it fits in my low garage door with the lift even. It’s real naaaace...
rover67
Rising Sun Member
and because before and after lift pictures are super fun:
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DaveInDenver
Rising Sun Ham Guru
LOL, there's more snow now than when you started.
rover67
Rising Sun Member
Finally got some time to tune the 1/4 wave antenna for the Ham radio.
I cut it long to start and worked my way down 1/4" at a time. I think I ended up at a pretty decent spot. at 144.520 Mhz its putting out 19W and reflecting 0.25W or so, it's hard to tell on the meter. So 1.26 VSWR? Doesn't change too much at 147.520. The only weiord thing I thought was that it was putting out 20W or so on the "H" setting. I thought that was low? The radio is a TM-V71a I think rated at 50W.
Anyhow, here are the numbers for the 1/4 Wave antenna on the roof. I just recorded my cuts (1, 2, 3, 4) and forward and reflected power. I actually just threw it in a spreadsheet to share, don't worry I wrote the actual numbers on a piece of cardboard with a sharpie
I'm not that geeky. In the end I also threw it on the fender mount just to check how that spot worked and got about the same final numbers.
I cut it long to start and worked my way down 1/4" at a time. I think I ended up at a pretty decent spot. at 144.520 Mhz its putting out 19W and reflecting 0.25W or so, it's hard to tell on the meter. So 1.26 VSWR? Doesn't change too much at 147.520. The only weiord thing I thought was that it was putting out 20W or so on the "H" setting. I thought that was low? The radio is a TM-V71a I think rated at 50W.
Anyhow, here are the numbers for the 1/4 Wave antenna on the roof. I just recorded my cuts (1, 2, 3, 4) and forward and reflected power. I actually just threw it in a spreadsheet to share, don't worry I wrote the actual numbers on a piece of cardboard with a sharpie
I'm not that geeky. In the end I also threw it on the fender mount just to check how that spot worked and got about the same final numbers.
rover67
Rising Sun Member
Weird, went back down there to make sure I didn't have the wrong insert in the Watt Meter and turned it on and keyed it back up after verifying that the insert was correct and I got 41W out and like 1W reflected. I wonder what changed. Maybe the high SWR before had the radio dialing itself back a bit.
DaveInDenver
Rising Sun Ham Guru
Can you get your hands on a dummy load? That's the way to check the radio's output. Also remember most ham radios are rated for 13.8V so there'll be a difference in output depending on the battery voltage, voltage at the radio, etc. When the engine is running the radio will probably do 50W but otherwise probably not.
rover67
Rising Sun Member
I'll have to get a dummy load. Yeah this was all done with the engine running (alt charging). I didn't measure voltage at the radio.
DaveInDenver
Rising Sun Ham Guru
Forgot to mention that it's possible the radio is folding back it's output. That shouldn't change the SWR (it is what it is) but it's easier on the radio to use the low power setting. You get the same antenna characteristics doing the measurement with mW as you do tens of watts.
DaveInDenver
Rising Sun Ham Guru
Where you stopped cutting is as good as it's going to be.
Why is that the best you can do? Because you're matching a 1/4λ whip with a characteristic impedance of 37 Ω to a 50 Ω coax. So the ideal SWR is 1.35:1. You're matched well across your intended range of frequencies and your low side hit it's minimum and has just started to rise indicating it's starting to become electrically shorter than ideal for the wavelength. So done and done.
Another measure you can do is bandwidth. In this case you don't have enough data to really see. Normally you'd measure the range of frequencies where the antenna demonstrates an SWR of 2:1 or lower. But in this case you can say that your antenna shows 3MHz of bandwidth or that it's got at least 2% bandwidth of SWR 1.4:1 with a center of 146.02 MHz.
If you going for perfection in this case you'd actually want to use a center of 146.00 MHz (since our ham allocation spans 144 to 148 MHz) and get the minimum SWR there. So strictly speaking you might still go just slightly shorter. Although it's possible you actually did nail the minimum for 146.52 already and might have cut shorter than ideal. Whichever, it's practically right on.
But since the bandwidth for this antenna is so very wide finding perfection is not necessary. Since hams have a fairly small 2m allocation it's not difficult to use one antenna for it all. Other bands this is not true. It's often not possible to cover the whole 70cm allocation with one antenna if it has gain, for example. It's also not possible to cover some of the lower HF bands with an SWR of 3:1 or lower with one antenna where the length margins are measured in several feet and not fractions of an inch.
FWIW, the specs for a Flexi-Whip (which are typical for a plain old 1/4λ monopole) are 18 MHz of bandwidth on 2m VHF, so tuning in 1/4" cuts is pretty forgiving. With a more complex antenna (with matching networks or coils) you'd probably want to use smaller increments because it'll be easy to miss the resonant length.
Why is that the best you can do? Because you're matching a 1/4λ whip with a characteristic impedance of 37 Ω to a 50 Ω coax. So the ideal SWR is 1.35:1. You're matched well across your intended range of frequencies and your low side hit it's minimum and has just started to rise indicating it's starting to become electrically shorter than ideal for the wavelength. So done and done.
Another measure you can do is bandwidth. In this case you don't have enough data to really see. Normally you'd measure the range of frequencies where the antenna demonstrates an SWR of 2:1 or lower. But in this case you can say that your antenna shows 3MHz of bandwidth or that it's got at least 2% bandwidth of SWR 1.4:1 with a center of 146.02 MHz.
If you going for perfection in this case you'd actually want to use a center of 146.00 MHz (since our ham allocation spans 144 to 148 MHz) and get the minimum SWR there. So strictly speaking you might still go just slightly shorter. Although it's possible you actually did nail the minimum for 146.52 already and might have cut shorter than ideal. Whichever, it's practically right on.
But since the bandwidth for this antenna is so very wide finding perfection is not necessary. Since hams have a fairly small 2m allocation it's not difficult to use one antenna for it all. Other bands this is not true. It's often not possible to cover the whole 70cm allocation with one antenna if it has gain, for example. It's also not possible to cover some of the lower HF bands with an SWR of 3:1 or lower with one antenna where the length margins are measured in several feet and not fractions of an inch.
FWIW, the specs for a Flexi-Whip (which are typical for a plain old 1/4λ monopole) are 18 MHz of bandwidth on 2m VHF, so tuning in 1/4" cuts is pretty forgiving. With a more complex antenna (with matching networks or coils) you'd probably want to use smaller increments because it'll be easy to miss the resonant length.
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DaveInDenver
Rising Sun Ham Guru
Wish this was editable, IH8 incomplete statements. The characteristic impedance of a 1/4λ monopole over a ideal ground is ~37 Ω. IOW, putting a whip like this in the middle of your roof will be essentially that.
The feed point impedance of a simple 1/2λ dipole is twice that, typically ~73 Ω.
Which leads to the next point, which is why you'll see construction of simple antennas that look like this:
The sloping ground radials (45° in this case) tend to make the feed point impedance close to 50 Ω since it's neither a 1/4λ over ideal ground nor a 1/2λ dipole. Technically speaking 42° will be exactly 50 Ω on paper but what's a couple of degrees, we're amateurs after all right?
rover67
Rising Sun Member
This is exactly why I quit cutting but rather than plot it I was visualizing it in my minds eye. It's nice to see it plotted, in fact that's how I may approach tuning my 5/8 wave antenna that I proceeded to cut too short right out of the gate. I am waiting on a new whip for it to replace the one I botched.
Also as a side not, the SWR of the antenna running 440.000Mhz was less than 2 which is kinda neat... I mean I know it's not a dual band antenna but good to see its reasonable?
Also, I appreciate the analysis and, in this case, the validation. I always wonder if I'm doing things right which is part of the reason I share what I'm trying....
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rover67
Rising Sun Member
That's good info, I always actually wondered why the radials were sloped downwards like that!
DaveInDenver
Rising Sun Ham Guru
Actually do the maths.
The wavelength of 146MHz is almost 3 times that of 440MHz. So a 1/4λ on 2m is 3/4λ on 70cm, roughly speaking. It'll have the same impedance but the radiation pattern will have changed is all.
It technically IS (or at least very close to) a dual band...
It's why bandwidth is important. The two allocations and band plans aren't exactly multiples. So you could tune the antenna for a particular frequency on one band and if it has enough bandwidth it might cover what you need on odd (this only works on odd ones) multiples on others. I don't remember off hand the frequencies that align but I *think* if you leave your antenna slightly long on 2m it'll cover the majority of simplex and repeaters on 70cm. You technically need about 433 to 450 so if you tune for 147.2MHz you should also be centered at 441.5MHz (e.g 147.2 x 3 = 441.5).
FWIW, these are generalized elevation radiation patterns. You see a 3/4λ antenna develops a null but gains energy in a lower lobe. The same would happen at 730MHz (5/4λ), 1460MHz (7/4λ), etc.
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rover67
Rising Sun Member
I need to read your previous post a few times to understand better.....
BUT I figured out why my radio was not pleased and cutting output. I have the APRS freq on the second side of the radio and it was running along with APRS Droid while I was tuning the antenna.... so removing it , cutting it, and reinstalling it. So, it was transmitting at times when there was no antenna installed and likely not super pleased about that.
BUT I figured out why my radio was not pleased and cutting output. I have the APRS freq on the second side of the radio and it was running along with APRS Droid while I was tuning the antenna.... so removing it , cutting it, and reinstalling it. So, it was transmitting at times when there was no antenna installed and likely not super pleased about that.