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View Full Version : Does anyone use 70cm while wheeling?


jonharis
01-18-2012, 06:48 PM
I'm getting ready to order my mobile rig and am looking for some advise. I've been perusing the forum here and on Mud trying to determine if a dual band rig is worth getting. I currently have a FT-270 which I've been listening to for about 4 months. (I'm taking my test the last week of Feb!). My primary reasons for having a vehicle mount rig are for trail use and emergencies. 98% of my time is spent in Colorado or Utah west of the continental divide. I've narrowed my options down to two and would like your input.

FT-2900R: It's 2M only, I like that the buttons are big and I won't get lost in the menu. I like that I have the option of 75W transmit in the event of an emergency. I like that it is very simple in construction.

FT 8800R: Has all the bells and whistles as well as 70cm. Does anyone really use 70cm around here? How bout cross band repeat? I don't really have a need for the remote faceplate.

Antenna options would be appreciated too. I think I plan on mounting the antenna to the Slee rear bumper in the upper position.

wesintl
01-18-2012, 07:22 PM
I have both and while I like the simplicity of a 2m only I prefer the independent 2 channel operation like the 8800. I have the FTM-350 for APRS. I haven't used 70cm much at all. Most wheeling is 2m.

I wouldn't buy the 8800 for just for 70cm though. Good thing is if you buy either one and decide you want the other they both hold their value and you can sell em here or mud no problemo.

DaveInDenver
01-18-2012, 07:39 PM
I use 70cm a fair amount. On commutes I've been hanging out on 449.450 and around the house/neighborhood we use 70cm simplex. I've also used the cross band repeat on my FT-8800 70cm in and retransmit on 2m. I wouldn't say it's necessary, but I like having it. Plus the more hams that use it the better, the lower UHF spectrum is constantly under threat of being reallocated as it's quite valuable for a lot of stuff.

I'm very interested in the FTM-350 and have been kicking around the idea of selling my FT-8800 and FT-1500 to roll the mobile and APRS into one radio and maybe eliminating an antenna off the truck.

smslavin
01-18-2012, 08:24 PM
I'm very interested in the FTM-350

This is what I have in the truck. Great radio but I'm still learning my way around it. I haven't spent too much time on 70. Most of the big repeaters here in the SD area, at least the ones I can get to, are pretty much 2m.

DaveInDenver
01-19-2012, 08:43 AM
This is what I have in the truck. Great radio but I'm still learning my way around it. I haven't spent too much time on 70. Most of the big repeaters here in the SD area, at least the ones I can get to, are pretty much 2m.
There's no doubt on the desire to get one, I'm convinced with the recent firmware updates (the radio can do NMEA0183 now) that it does everything I'd like. But the $600 price tag is steep. I guess if I got $100 for the FT-1500 and $300 for the FT-8800, maybe I could swing it tho. Can't forget the 'extras', GPS module and programming software... :doh:

pskhaat
01-19-2012, 09:55 AM
Dave, you're selling your 8800?

As of several years ago, I would only be able to reach 70cm repeaters in the Western Grand Canyon area, nothing on 2m, so I appreciated the option of both.

DaveInDenver
01-19-2012, 10:05 AM
Dave, you're selling your 8800?
Just kicking ideas around. I'd definitely have to sell it to get a FTM-350. I have a second radio for APRS, an older FT-1500 with a TinyTrak4 and Garmin GPS thanks to KD0FDS, and 3 antennas (2 x VHF and 1 x UHF). It would be nice to eliminate an antenna and have a single radio.

smslavin
01-19-2012, 10:11 AM
There's no doubt on the desire to get one, I'm convinced with the recent firmware updates (the radio can do NMEA0183 now) that it does everything I'd like. But the $600 price tag is steep. I guess if I got $100 for the FT-1500 and $300 for the FT-8800, maybe I could swing it tho. Can't forget the 'extras', GPS module and programming software... :doh:

I'm a rev or 2 behind on the firmware. I need to update. The extras floored me when I went into HRO to pick it up. You want how much for that cable? :rant: But, it gives my wife piece of mind when we're out in the boonies with the kids so it's all good.

pskhaat
01-19-2012, 10:15 AM
Well, let me know on the 8800. I had my 8900 head unit stolen out of my vehicle some time back. I'm debating either replacement or picking up a used radio (nearly the same $) but don't honestly need 6m & 10m FM ...

jonharis
01-19-2012, 10:19 AM
Well Thanks for the replies.

The one reply stating that 70cm is sometimes the only repeater available (dependent on the area) is making me lean towards the 8800. That's going to make me change my antenna choice as the firestik is only for 2M (liked the idea of matching antennas but function is more important than form). We do a fair amount of traveling and I do end up in AZ, NM and NV a fair amount also. I should have stressed that a primary concern for me is safety, I want as many means of communication as possible. We often travel solo to areas that only get a few vehicles annually so having flexibility might be worth the increased complexity.

CardinalFJ60
01-19-2012, 10:28 AM
Well, let me know on the 8800. I had my 8900 head unit stolen out of my vehicle some time back. I'm debating either replacement or picking up a used radio (nearly the same $) but don't honestly need 6m & 10m FM ...

So.....if you decide to sell the 'brains' of your 8900 I might be interested. I have an 8900 in my 60, might be cool to have the same at in the shack or in my 40. I'm sure I could move faceplates back and forth.

OH wait...just re-read...sounds like the whole thing got nabbed, not just the faceplate.

MDH33
01-19-2012, 10:45 AM
I had an 8800 in my 40 and decided to sell it and use a 2900 instead. I never used the 70cm and although I miss being able to listen to both the simplex and repeater at the same time, I don't miss how tiny and delicate the 8800 seemed to be compared to the 2900. The 2900 is much better suited to being in an open 40. I put a 2800 in my Hilux as well. They are both easy to use, easy to see, and have tough construction. I also like the higher power of the 2900 and 2800 for peace of mind when I'm far away from repeaters and cell coverage.

nakman
01-19-2012, 10:00 PM
As I've said like 8800x now, I have the 8800 and love it. But I'm curious where you'd mount a 2900 in the 100- the remote face seems to be the default for the 100 series setups, mainly due to lack of space, or not wanting to bolt on a knee buster.

and to answer the original question, I've only used 70cm once just to say I did.. but I'm on two 2m channels all the time. http://www.risingsun4x4club.org/uploads/smileys/tinfoilhat2.gif

jonharis
01-20-2012, 11:15 AM
Thanks Nakman-
Center console big enough for the 2900? I assume most controls can be operated via mic buttons. I would do an external speaker on the passenger side. Heat issues? I don't want a knee buster for me or passenger. For a remote setup, I really like the use of the sunglass holder but :Princess: won't let me. Somewhere on the dash would have to work.

And one more probably dumb question. Is it possible at all to use 70cm with a 2m antenna? even at a reduced capacity?

nakman
01-20-2012, 11:54 AM
I can see this weekend if a 2800 will fit, I have one that's not installed in anything right now. I believe it's the same size radio. Yeah heat is a concern, but others seem to be doing it with no ill effects, so :confused: your call on if it's an issue. Depends on how much you transmit, and at what power, and how well tuned your antenna is... kinda hard to get a straight answer. IMO the remote faceplate under the heater is best, with the head unit either under the passenger seat or behind the back cargo panel.

And yes, you could technically blast any frequency through any antenna with some reduced capacity, sure -think of all the home brew antennas out there. But the performance loss on transmitting gets converted to heat, which in a worst case would potentially let the smoke out of the radio? I'm sure a few transmits you'd be fine, but prolonged use probably not a good idea. It's easy enough to get a dual band antenna in the first place though, I think the SBB-1 goes both ways and it's a cool little stubby for trails.

DaveInDenver
01-20-2012, 12:47 PM
And yes, you could technically blast any frequency through any antenna with some reduced capacity
NO!

The relationship of 145MHz to 445MHz is such that they do not share a 1/4λ multiple fundamental. If you key on 70cm into a 2m antenna it's probably going to see a high reflection.

There are ways to make this work, a gamma match or making the antenna into a sleeved dipole, etc. But typically mobile monopole whips use a trap to make a long antenna electrically correct for 70cm, say a 1/4λ 2m into a 3/4λ 70cm or 1/2λ 2m into a co-linear 70cm.

All solid state radios made now necessarily (tube radios tolerate high SWR much, much better) shut down on high SWR, which is why you could probably key up and not ruin your radio. It might even leak a little RF onto the antenna, but it won't be much (like milliwatts).

If you do it long enough with high enough power, you'll fry the protection shunt. It's all about heat, any power not doing work exciting electrons (which requires antenna resonance or apparent resonance with caps and inductors helping) is converted to heat, which is the sworn enemy of transistors.

jonharis
01-20-2012, 12:57 PM
Wow, thanks for the lesson in radio frequency theory.

I like that little SBB-1. I look forward to hearing about the fitment of the radio.

Just found this great thread on Mud that I think I might try to copy after hearing your advice.

http://forum.ih8mud.com/80-series-tech/219388-yaesu-7800r-diamond-k400c-comet-sbb-1-install.html

nakman
01-20-2012, 12:59 PM
Dave I'm not sure we're saying different things.. as you still say it's technically possible, but not a good idea. agreed.

But if you were transmit on 70cm with a 2m antenna to a truck that's is 50' behind you, I'm not sure he wouldn't hear you. We can try with one of your radios.. :)

DaveInDenver
01-20-2012, 01:06 PM
Dave I'm not sure we're saying different things.. as you still say it's technically possible, but not a good idea. agreed.

But if you were transmit on 70cm with a 2m antenna to a truck that's is 50' behind you, I'm not sure he wouldn't hear you. We can try with one of your radios.. :)
You are very right that for RX the 2m antenna would be marginally different in the real world than a tuned antenna on 70cm. It's possible that a 5/8λ 2m might even receive slightly better than a proper 70cm.

I read that this was for TX on 70cm potentially using a FT-8800 with a 2m-only antenna since the FT-2900 does not even receive 70cm. That would not be a good idea at all.

The RF that comes out would be due to the incidental and reflected waves on the coax itself. The antenna wouldn't be doing much work. In reality it would almost the same radiated energy you get from a dummy load, which works BTW. Running 100W into a power resistor or even an incandescent light bulb radiates energy and you can actually hold a QSO using a light bulb as an antenna if band conditions are good. It takes quite a bit of power to do that and the field you generate is about equivalent to a super QRP radio into an tuned antenna (think 200mW).

CardinalFJ60
01-20-2012, 04:19 PM
so...when Martin, Perry and Sean were guiding me down to Blue Notch the 2m signal would come and go based on the part of the canyon I was in, how deep/tall is was, etc. Makes sense.

The discussion then started about whether or not 70cm would have been more effective since it would tend to 'bounce' a little better. I think it would have been a little better but we never tried it.

What say ye??

rover67
01-20-2012, 04:39 PM
YES! YES!!

I want to talk about how 70CM propagates in canyons compared to 2m. Maybe the topic for a different thread? I had a nice conversation about it with Nathaniel at Blue Notch last year and am thinking maybe we should switch freq's when we are in tight terrain? at least try it once?

subzali
01-20-2012, 04:54 PM
I have been thinking the same thing Marco, but have never actually tried.

dr350jja
02-01-2012, 08:19 PM
Are there simplex channels on the 70cm band?

DaveInDenver
02-02-2012, 06:36 AM
Are there simplex channels on the 70cm band?

For Colorado:
http://www.ccarc.net/images/CCARC_FUP_420-450MHz_revd.pdf

This should be similar most places AFAIK, I don't think there's any band plans that use other than 5MHz splits and 25KHz spacing for analog voice.

There are 24 simplex FM, 119 5MHz repeater pairs, 59 aux 5MHz repeater and whole bunch of narrow band (digital) 12.5KHz simplex, pairs and data. There is 30MHz of spectrum allocated to amateurs that is (1) VERY commercially desirable and (b) largely silent.

Use it or lose it!

FM simplex:
445.700, 445.725, 445.750, 445.775, 445.800, 445.825, 445.850, 445.875
445.900, 445.925, 445.950, 445.975, 446.000, 446.025, 446.050, 446.075
446.100, 446.125, 446.150, 446.175, 446.200, 446.225, 446.250, 446.275

Bold is unofficial National Calling Frequency

For comparison hams have just 4MHz of spectrum on 2m and have to cram repeater splits on 600KHz. This makes repeaters expensive and touchy to tune.

dr350jja
02-02-2012, 09:38 PM
(I'm a new ham, so I don't have a firm grasp on how this all works yet)

I was curious about the simplex on 70cm, because I noticed you showed 2m simplex in a sticky thread:

RS#1--146.460
RS#2--146.580
RS#3--147.420
RS#4--147.540

Just wanted to see if you use simplex on 70cm. If I read this correctly, it sounds like the 70cm is better to use in the mountains than the 2m??

nakman
02-02-2012, 09:59 PM
We have 4 channels designated for 2m since that's the most common radio, particularly in mobile rigs (2m), which is all most were getting when the club first got into ham radio. There currently isn't a designated Rising Sun 70cm frequency, and while there could easily be it wouldn't apply to likely 60% of our licensed operators here. not because of band privilege, but equipment.

And yes, you hit it the theme of the thread here is exploring just that- does 70cm propogate better in the mountains (and canyons) than 2m.. and my answer is I don't know, but I'm willing to try!

RockRunner
02-02-2012, 10:41 PM
We have 4 channels designated for 2m since that's the most common radio, particularly in mobile rigs (2m), which is all most were getting when the club first got into ham radio. There currently isn't a designated Rising Sun 70cm frequency, and while there could easily be it wouldn't apply to likely 60% of our licensed operators here. not because of band privilege, but equipment.

And yes, you hit it the theme of the thread here is exploring just that- does 70cm propogate better in the mountains (and canyons) than 2m.. and my answer is I don't know, but I'm willing to try!

So Tim, let's try a 70cm channel tomorrow and see how it works. I will monitor 460 and the denver repeator for any RS members. If you are out and about we can try 70cm just LMK what channel. I will be on the south side of town so not sure of reception.

nakman
02-02-2012, 11:19 PM
Alright if I get called out I will definitely give you a shout!

DaveInDenver
02-03-2012, 06:14 AM
does 70cm propogate better in the mountains (and canyons) than 2m
No, it does not and that's the point. It is more easily absorbed by terrain and does not multipath as badly as VHF, is less likely to duct in the troposphere, so less interference and less chance for random DX. The low side of UHF is more VHF-like than VHF.

Like I mentioned, I usually ragchew on the RMRL's 449.450/-5MHz/103.5 and I suggest using 446.000MHz simplex if you want to check paths since there might be people listening on that.