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Author Topic: Highest power HT?  (Read 18636 times)

Posts: 14492

« Reply #15 on: September 02, 2010, 05:36:07 AM »

In most cases you'll get more "effective gain" by replacing the typical rubber duck antenna with something better than you will by going from 7W to 25W - and it will receive better too.

Bob  AA4PB
Garrisonville, VA

Posts: 490

« Reply #16 on: September 02, 2010, 06:24:29 AM »

I'm sure one could be built, but I'm guessing the market for such a monster would be very small.

I have a Kenwood TM-271a Mobile which is a simple moble and is 80% heat sink. I could imagine it to be reformatted into something the size of a very large handheld (e.g. some of those old CB radios) and weigh about 2 pounds (before battery). A 25W out, it'll probably draw 4-5 amps during transmit so, even if you only used "Super-Hi" power occassionally, you'd still need a battery pack that would survive high current draws, even if only momentarily. So, your looking at something like a LiPo technology (like what is used by Electric RC cars and helis), which is expensive. And even if you said "25W for emergency only," some (most) would complain that it wouldn't be worthwhile unless you could do it for a while, which means a bigger battery.

So, while none of this is rocket science, you end up with a heavy and expensive brick hanging from your belt or harness.

Now, with VHF, the antenna placement is much more important than the raw power out, so I'm thinking that 25 watts into a (beefed up rubber duck) held up to your head or hanging from your waist isn't going to go much further than 5 watts. If you are going to put an external antenna on the radio to take advantage of the power, then you're might as well use a mobile radio hooked to an external battery. Or, just put a better antenna on your existing 5W handheld (I've made 80-mile QSOs from a handheld into a good mobile antenna.

So, I'm sure you could make a 25W handheld, but why bother?


Posts: 1454

« Reply #17 on: September 02, 2010, 07:04:52 AM »

Having carried those brick radios and all the other law enforcement gear, I can tell you that not only did weight you down when running after suspects, but many officers ended up with curved spines in the direction of the greatest weight. In my case, I tried to balance the radio and other stuff out with a S&W .44 Magnum. Unfortunately, my spine curved in the direction of the S&W and has stayed there ever since.  Sad

Posts: 14492

« Reply #18 on: September 02, 2010, 01:25:59 PM »

Many of the new mobile radios are getting pretty small. Why not put one in a back pack along with an appropriate battery and antenna?

Bob  AA4PB
Garrisonville, VA

Posts: 5639

« Reply #19 on: September 03, 2010, 02:06:34 PM »

I understand Icom makes some 7W HT models, but the effective gain between 5W and 7W is really negligible, and it's why I said "about" 5W in the original post.  I still think a modern 25W Mosfet-based HT is do-able, and could be made about the same size as the average business hand-held of 25 years ago.  You know, those old low-VHF Motorola talkies that police used to have clipped to their belts in the 80's.  When I was a kid, our local police department operated on 39.020 MHz, and their radios were about the size of a small red building brick.  Probably weighed the same, too, with half of that weight being the NiCad pack.

With the other half being the frame everything was mounted inside. Smiley

I've seen more than one of those that had been run over by a vehicle with no noticeable damage OR decrease in performance. I'm also familiar with a couple of incidents where they became a "non-lethal" alternative with a baton wasn't available. Smiley

A smoking section in a restaurant makes as much sense as a peeing section in a swimming pool.

Posts: 131

« Reply #20 on: September 04, 2010, 09:05:04 AM »

You can do it! Just buy a HIGH POWER dual band mobile & a deep cycle marine battery & head out.That is why it is NOT possible today.The BATTERY or POWER source would be the issue,NOT the radio! Hope you have a GOOD BACK! }:>)

W4KVW Grin

Posts: 5688

« Reply #21 on: September 04, 2010, 05:29:14 PM »

I once hopped up the output of one of those old Motorola HT's that had been converted for 2 meter use.  Got about twelve  watts, measured into the shop dummy load on the Bird. 

However, the doggone thing would give you these funny headaches when attempting to use it in QSO for more than a few seconds.  I wasn't the only one who complained of that, either. 

It hurt the eyeballs, no kidding. 

Battery life was rather short when on the high power setting, even with extended packs. 

But that eyeball thing was the reason for abandoning that notion.

The damn thing could make ya nauseous. 


Posts: 1561

« Reply #22 on: September 08, 2010, 07:38:56 PM »

25W portable..

Find a good used HTX252, that a RS 25W mobile thats just plain tiny.

Add a antenna. you have to find on that can stand 25W.

Battery, 7AH gell cell, net weight 4.6 pounds!  RX operating like about
6 hours, TX full power 20 minutes total (maybe less).

Find a way to get the RF out of the MIC as it will be impossible to keep
far from the antenna.

And since the usual limiting factor is antenna height and antenna quality
you range for that kluge will be only slightly better than a good 5W HT
with a ground plane on a 12ft collapsible fish pole.

A rubber duck has negative gain. One of the 15" jobs will be better
and they do make longer ones!

I've demonstrated a RS HTS245 dual bander a whopping 1.5W using a
39" tall end fed halfwave (ARRL, mobile manual and antenna compendium)
for repeater contacts out to 12-15miles.     If I strap that antenna to a
12ft fish pole (breem or crappy collapsible) the range is even better.   At
VHF it's height and since good antennas are still moderately small that helps.



Posts: 46

« Reply #23 on: October 01, 2010, 08:18:32 PM »

Why not use a 1W, 50-pound linear in your car? Or a big antenna fed to a deaf receiver?

As you will learn about communications, your most effective gains are in antenna system and antenna height, especially on VHF/UHF.

Many public-safety organizations use in-vehicle UHF/VHF crossband repeaters, which any ham can use if their licence permits.

I don't know what the point of a 25W portable would be. Perhaps you could be heard, but often you couldn't hear, especially within a building with a crummy rubber duck.

You would be much better focusing on how to improve your antenna situation than to worry about output power. I have been amazed at how well a ground 1/4 wave counterpoise will work on an HT. It looks goofy, but greatly improves performance. A telescopic 1/4 wave works great for an HT too. Isn't there a legal requirement to use the minimum power possible to maintain a radio contact?

Posts: 1279

« Reply #24 on: October 03, 2010, 01:13:06 PM »

Hello, Watts the problem. $119.00 gets a Mirage HT amp for 2 meters that puts out 35 watts. Works on FM and SSB.  It works from 12 volts and has an RF receive amp as well. Hook up a 12 volt gel-cell make a carry holder for the amp and the battery and your set to go. I do not see any reason for this much power on 2 meters or 70 cm. My HT will hit just about any repeater I can hear, and that's why I bought it. If I need a high power system I would buy a Mobil 100 watt VHF/UHF portable.

Just a note, If you want you can buy a 25 watt high frequency amplifier on an IC for not to much money. We used them many years ago on a navigation beacon on 421/441 MHz. Never had a problem with them, and the circuit wiring  is minimal. One of the joys of Ham radio is the ability to experiment. Lay out a 25 watt hand held circuit and see what you can come up with. Might even be marketable who knows.


Posts: 89

« Reply #25 on: October 04, 2010, 09:04:31 AM »

i took the proposal and made up a bag radio  with a yaesu ht a 50 w amp and a large gell cell, the ht can operate on internal batteries, external batteries, with it own antenna or the antenna attached to the bag, i can remove the ht to work on it own, it also has some jumpers and a cigarette lighter plug that will power the system from an auto battery , the antenna attached will attach to an auto window so i can adapt it to any car or truck, so this can be down, it weighs about 10 lbs all together but is portable enough and powerfull enoughh to reah some diatant repeaters.  i used an army butt pavck and shoulder strap to carry the whole  deal.



Posts: 1003

« Reply #26 on: October 17, 2010, 07:15:07 PM »

If the 5W setting on your HT isn't getting heard where you need to be heard, you either change your location (get out of the building, or out of the gully) to where your signal isn't being blocked, or use a more efficient antenna - if you're using the stock 'duck' that came with the radio, get a better aftermarket antenna (it WILL be a lot longer than the 'duck'), use a counterpoise with the duck or other antenna, or use something like a Jpole or an lightweight beam (ELK and Arrow make some) and a painter's pole or tripod setup to get it up into the air.
If you've ever used an HT extensively on the 5W setting, you'll know that it gets quite hot.  You'd need barbecue mittens to hold onto a 25W HT.  If you regularly operate from inside a building, and have trouble getting a signal out, consider putting an outside antenna on the building, if that's feasible and allowed. Work with the building maintenance people to run the coax properly.

Fred Wagner, KQ6Q

Posts: 680

« Reply #27 on: October 19, 2010, 09:35:21 PM »

"Answer: Nothing. Radios under 50W PEP and mobile/portable stations using PTT control are exempted from the RF exposure requirements."

not precisely true. You're still legally obligated to do the analysis, etc., but being in certain power and operating ranges makes the analysis simple, because you can use the "safe harbor" sort of approximations. But you'd still have to document that you met the assumptions.

Watch out for the "multiple transmitter" rule though.  A HT and a cell phone make for multiple transmitters, with both transmitters being greater than 5% of the total power.

I'd not want to get into an argument with a regulatory agency about it.
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