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TOPIC: Worth Sharing

Worth Sharing 8 years 2 months ago #201

  • Asad Khan AP2ASD
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I raised the following questions on eHam forum and was given the following answers. FYI

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Icom 706MKIIG Reply
by KC2VOB on September 7, 2009 Mail this to a friend!
Hi All,

Why is it that multi-band radios have very little output power on 2m/440?

If not illegal, is it possible to modify IC-706MKIIG to put out 100w on 2m and about 50w on 70cm? It's ok with me if that would result in lesser power on HF.

Is it ok to keep a radio on top of power supply?

73,
KC2VOB

RE: Icom 706MKIIG Reply
by N3OX on September 7, 2009 Mail this to a friend!
"is it possible to modify IC-706MKIIG to put out 100w on 2m and about 50w on 70cm?"

No, of course not. If that could be done, it WOULD have been done... manufacturers don't hobble their PA sections by 3dB or 4dB arbitrarily. In fact, if anything, they probably push the devices a little hard and accept a little more distortion than they maybe should. 100W 2m / 50W 70cm would be a huge selling point.

The reason why these rigs have lower power output on VHF/UHF is because it's harder and more expensive to do higher output efficiently on VHF/UHF than it is on HF. You have to consider current draw and thermal issues... you have to worry about having too much VHF/UHF gain in a small box because you can get oscillations.

Amp or antenna are your options for more oomph...

73
Dan

RE: Icom 706MKIIG Reply
by N3OX on September 7, 2009 Mail this to a friend!
"Is it ok to keep a radio on top of power supply? "

Sure, more or less. The only issue is that it makes the ambient temperature around the radio higher. I doubt it puts it out of spec though...

RE: Icom 706MKIIG Reply
by KZ1X on September 7, 2009 Mail this to a friend!
Q. Why is it that multi-band radios have very little output power on 2m/440?

A. I think what you really men was "why do rigs like the IC706 put out less power on VHF/UHF than they do on HF?" and the answer is, in general, cost. To generate the same 100W of RF power, in the frequency range you mention, would make the rig much more costly. And another reason: you don't need the power ... read on ...

Q. If not illegal, is it possible to modify IC-706MKIIG to put out 100w on 2m and about 50w on 70cm? It's ok with me if that would result in lesser power on HF.

A. Well, you could always add on another external amplifier if you wanted to. It's not illegal for an amateur to modify a radio to do whatever you want, as long as emissions standards are adhered to, it's just not practical to do as you suggest. First off, the gain of the output devices falls off with increasing frequency (it's a matter of physics) and then there are packaging issues, dissipation, coupling, bandpass ... it would require a wholesale redesign of the radio.

Moreover, the real issue is, RF transmitter power isn't the limiting factor in your station performance. That limit is substantially set by your antenna. On HF, getting gain can be tough, a 20 meter Yagi is pretty big! so 100 watts to a smaller antenna with a gain of 1 results in 100 watts effective radiated power. Good for HF work, where the tropospheric propagation does not predominate. The same size antenna on 2 meters would have perhaps 16 dB gain. So if you put in 50 watts into that antenna, your effective radiated power would be ...

... 1214 watts !!!

So, as you can see, transmitter power is only a small part of how well your station works. Don't forget: your receiver is also a part of the station. There's little point transmitting to someone you cannot hear.

Q. Is it ok to keep a radio on top of power supply?

A. There are three issues here, that I see. The big one is thermal ... would doing as you suggest limit the cooling of either the power supply or the rig? Further, do you want to add to the heat of the radio by putting it next to a power supply which also has dissipation? The next issue is magnetic fields. Some rigs are sensitive to the strong magnetic field of a nearby linear power supply, if you are using one. Lastly, ergonomics play a role as well. Would access to the rig's controls be affected by placing the rig above the table height?

RE: Icom 706MKIIG Reply
by WG7X on September 7, 2009 Mail this to a friend!
It is very simple:

Most RF transistors develop less power at higher frequencies. Transistors that make more power on VHF and UHF are more expensive. That's why most manufactures use transistors that don't make a lot of power at VFH/ UHF.

That is also why you have separate connectors for the HF/ Six meter and VHF/UHF on the 706. There are two sets of finals in that rig, one for HF and low VHF the other for VHF/ UHF.

Do yourself a favor: If you really need more power than the rig alone can provide acquire an external amplifier. Monkeying with the finals in the radio will only bring you grief and expensive repair bills. Short of an external amplifier there is NO WAY that the 706 will ever come close to the power levels you asked about.

When you begin to shop for and price out the VHF and UHF amplifiers, you will begin to understand why the makers did it the way they did. High power at VHF and UHF is expensive!

Than, maybe you will also ask yourself why you were so concerned about higher power in the first place...

High power at VHF and above is usually the domain of weak-signal work and not necessary or desirable in the repeater areas. If you were into weak signal work, you probably would never have asked that question, or if you did it would have been asked on a different forum in an entirely different way.

No trying to be difficult, just trying to help you understand why things are the way they are.

73 Gary
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Re:Worth Sharing 8 years 2 months ago #202

  • Riffad Khan AP2RF
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Dear Asad Bhai

wait----and try New IC-9100

will get answer of all of your concerns and interests.

This is ICOM latest HF 100W, VHF 100W ,UHF 75W , 1.2GHZ 10W RIG all in one RIG with D-Star.

Pre Released Info : www.ab4oj.com/icom/ic9100/main.html

73s

AP2RF
Muhammad Riffad Khalid
AP2RF
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Re:Worth Sharing 8 years 2 months ago #204

  • Asad Khan AP2ASD
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Rifad Bhai,

Thanks for talking. There’s a model already in the market – Kenwood TS 2000 – but it’s too large and heavy to be taken back and forth between the US and PK. With given specs, looks like 9100 will weigh as much as TS 2000 and cost more. It seems to be a blend of 910H and 746Pro. It’s intended to generate 100/75w on V/UHV for working satellites and will probably lack repeater offset feature like 910H. HF-wise, it looks like 746Pro which inherits transmit malfunction in its lineage. It will cost a signifant amount to send it to Icom for warranty repairs. AI4QT, a YouTuber, has sent his several times. Not having technical background I’m looking for plug-and-play equipments. Got no interest to perform experiments or get to know what’s inside a radio. I only like to transmit and receive.

Due to its clear audio and fancy features I see myself buying IC-7000. Initially I was considering 706 but it is prone to intermod and QRM. What makes me think twice is both of these go hot and I blame their compact sizes for this problem. They could have been 10lbs instead of 5 and would still fit portable use. I recently realized that I have bought too much gear while I am a casual ham. That’s why I’m selling everything I have and badly looking for one all-mode all-bander with a tuner though I am more into VHF like all other Pak hams. Some if this may be irrevalent but good intro.

Asad
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Re:Worth Sharing 8 years 2 months ago #207

  • Riffad Khan AP2RF
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Dear Asad Bhai

IC-7000 is the best Rig available in the market and Far Superior than IC-706 Family. It is mini IC-756PROIII.

It is under my use and I really like that rig.

You are very right ...its goes hot soon ... so I am very careful in using that Rig ….but I understand that these compacts rigs normally goes hot soon and after some modification on fan side one can somehow take control of that issue.

I would like to put your attention on FT-897D that I think the most compromised RIG for Radio Amateur.

I have used that rig as well and many AP HAMs are using that rig with great pleasure.

Great and Excellent Features like

1) Compact
2) Large 2 internal cooling fans so Never Heat Up
3) Can be used as Mobile with internal battery packs.
4)Versatility of using COLLINS SSB & CW filters + 2 internal battery packs to avoid carrying batteries.
5)ATU can be attached with the main unit and you can carry it as one unit.

6)Options can be purchased later as per the convenience.


In my opinion Price + Features + Performance = FT-897D and I have not seen a single issue in that rig specially its new version with RD70HVF1 and greatly improved HF finals.

No need to Buy any Rig after FT-897D and I will highly recommend it to all friends and new commers .Save your money

73s

AP2RF
Muhammad Riffad Khalid
AP2RF
Last Edit: 8 years 2 months ago by Riffad Khan AP2RF.
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Re:Worth Sharing 8 years 2 months ago #208

  • Riffad Khan AP2RF
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Final Stage Picture of the latest FT-897D

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Muhammad Riffad Khalid
AP2RF
Last Edit: 8 years 2 months ago by Riffad Khan AP2RF.
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Re:Worth Sharing 8 years 2 months ago #209

  • Asad Khan AP2ASD
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You know what Riffad! I don't like Yaesu's for some reason. I think I'm concerned more with the look rather than performance. In fact no body seems to be happy with Icom HF's, except for those novices who open the box upon receipt and post a review on eHam, giving the equipment 5 out of 5. Such reviews are based on the user's excitement, not experiment. Having spent $1,200 on a piece of equipment, I’d evaluate it for a year before I post a review. As of this day IC-7000 got mind-boggling 240 reviews of which very few are considerable. There’s a new HF/6M by Kenwood coming up early next year. I so much wish Kenwood has added VHF to it. May be I should wait for this one and may be this is what I want. For now we’ll continue with VHF junk. Do you do HF/6 meters? If so, at some point we can work Swabi and Faisalabad. That would be more fun than the standard 2 meters and Echolink. Oh…for some reason just the name Echolink pisses me off.

Asad
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