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Author Topic: ft-857 vs ic 706 MkIIG  (Read 4143 times)
N3OX
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« Reply #15 on: October 09, 2008, 09:28:00 PM »

"I don't argue the point that the differences between the two Yaesu models are slight to the casual observer."

In the case of those two particular Yaesu models ('857 and '897) I'm not sure you could tell which was which from their schematics or if I laid the bare mainboards out on the table.

QST rolled the reviews of the D models of the two rigs into a single review.

They're really the same radio in different boxes.  Maybe there are a couple of different buttons or knobs, but there seem to be no substantial electrical differences between the two rigs.  It's not just about the features.  I've done some of DG2IAQ's FT-897 mods on my FT-857 and the boards are practically identical... and I only qualify that with "practically" because I haven't gone component by component over the parts list for each radio, I'm just going by circuit diagrams, board layouts, and photos of a few square inches of board ;-)  Maybe the speaker in the '897 is better?  I dunno.  Certainly the display on the '857 is smaller.

"About the same scenario is happening as we speak about the 7000 vs. the 7200. They are not the same radio by any stretch"

Your point is well taken as a general one, but when we're talking about the Icoms, are we talking about two radios with the same circuit on the same board layout here?

I think it's germane in the context of the original topic because the '857 should work exactly the same as the poster's '897 in terms of things like receiver performance, transmitted audio, noise blanker and DSP functions.  I think an A/B test between an FT-897D and an IC-706 would be a fair surrogate for an A/B test between an FT-857D and an IC-706

I see what you're saying about other rigs... they can seem very similar to the casual observer and still have big differences in some aspect of their operation, but I think the two Yaesu rigs are really the same thing at the board level, and the differences are awfully superficial.  Maybe you know something about them I don't, but I've been inside my '857 working with of diagrams of an '897...

73
Dan





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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
N3OX
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« Reply #16 on: October 09, 2008, 10:08:51 PM »

"Regarding the filters in the IC-7000, what exactly do they do? Are they just like an EQ where it reduces some of the freq to reduce noise?"

No, it's not to reduce the noise you hear, it's really a basic necessary operation in receiving radio signals.

Think of it this way.  A lot of what a radio does is amplify signals ... eventually it demodulates them, but an important aspect is that you need a LOT of gain to get faint radio transmissions up to audible levels.

A pretty typical minimum detectable signal for a radio might be a tenth of a microvolt, maybe a bit bigger. You need a couple volts into a speaker to get good audio output. So you might have to increase a weak  signal's voltage by a factor of ten million. If you were just amplifying one signal on one frequency and there were no other signals, you could just use a chain of amplifiers that gave you a gain of ten million.

But the problem in radio applications is that there are other signals, all over all of the bands.  I can plug an antenna into my oscilloscope and get about 100mV pk-pk worth of an AM radio station on 980kHz here.   If I just had a simple broadband amplifier followed by a demodulator, and I had the gain cranked up to ten million, I'd need to be able to swing a million volts on the output of that sucker to linearly amplify the sum total signal, AM 980kHz + whatever weak signal I'm listening to.  

What really happens in that case is that the amplifier just clips hard at a 980kHz rate, doing very weird things to the, say, 14MHz signal I'm trying to listen to.  So what I really need to do is knock down the 980kHz signal by a factor of a million or more so my radio can actually amplify weak 14MHz signals in the presence of giant AM radio signals.  That's what the *RF bandpass filters* in the radio are for.  That's not really what you're talking about, but let's go there next.

IF filters perform a similar task, but they do so for *in band* signals.  You can't really use an RF bandpass filter to filter out that 59+30dB guy 5kHz up But he could cause the same trouble to your radio's circuitry that AM 980 causes to my simple dumb amplifier.  It's just too much signal for the rig when you're trying to listen to a weak one.

So, rigs convert the signal to a frequency where it's easier to do *very sharp* filtering.  In the case of conventional analog radios, a typical thing to do is use something like a crystal or mechanical IF filter, which drops off very steeply outside of the passband you're trying to listen to.  So that guy 5kHz up gets knocked way down, and you can use enough gain to hear your weak signal in the passband.

A DSP IF filter performs the same function, but instead of using some analog parts, it digitizes the IF signal while it's still at a pretty low level voltage-wise, stores it as a set of numbers, does some mathematical operations on those, and spits a new set of voltages out the other end based on the results of its calculation.  

There are all sorts of digital filters that operate on sampled data, and implementing different ones is just a matter of changing the math that's done in the DSP chip.  Once you've done this calculation to remove the really loud guy 5kHz up, and converted back to an analog IF voltage, you can go ahead and amplify the signal up more without overloading anything.

When implemented well, this is great, because you can just command the chip to do whatever filter you think you need at the time.

- - - - - - -

Anyway, all this filtering is basically to balance your need with huge gain to hear weak signals with the fact that there are loud, sometimes extremely strong, signals nearby.  All HF rigs have to have some of it, your '897 has a 2.4kHz ceramic resonator IF filter in it, but you can purchase optional ones to do narrower filtering.  The '897 also allows you do do some filtering at *audio* frequencies, but that doesn't work so well to narrow down the passband in the presence of strong signals because of the way the radio controls the gain when you *do* want to listen to a strong signal.  If you've ever tried the audio DSP CW filter in, say, a contest, without a real narrow CW IF filter, you'll see the problem.   Filtering as soon as possible before too much gain has been used on the signal is very important to getting good dynamic range in a receiver.

Anyway, a well-done IF-DSP shouldn't require much in the line of optional filters, basically because it's easily reconfigurable.  

The audio DSP in an '897 or most other rigs is really best used *after* proper IF filtering for the appropriate mode, and the audio DSP really is just for final tweaking.

73
Dan











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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
KF6HHH
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« Reply #17 on: October 10, 2008, 07:53:56 AM »

Thank you very much for taking the time to Elmer me on the filters.  This info was very helpful.  My background is more in recording engineering than E. Tech, which I have a limited background in (and I'm no recording engineer either, just a hobby).  

Thanks to you good folks my education in Ham is growing daily.  I'm reading my ET and Ham books again, so this explanation really helps clear things up.

73
The other Dan
Dan'o  :}
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NI4Z
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« Reply #18 on: October 10, 2008, 01:55:10 PM »

Hello,

I have an FT-857 (not a D) .  I sold an IC-706MK II G to purchase it.  I had a "screwdriver" type antenna that I used with the 706. I had various troubles from the 706 just shutting off to feedback in the vehicle radio speakers.  Another complaint I had was the way the menu system in the 706 worked.  I was never able to become familiar with the menu paths.  The display in the 706 is larger, and is easier to see.  Some of the features however do not work on both HF and VHF.  The SWR function is one of those.  

I purchased the FT-857 and an ATAS 120 antenna which is matched to the radio and will tune the antenna through the coax cable.  I have found the 857 easier for ME to operate.  I have had little trouble with the menu system.  I will insult no one's intelligence on this forum by trying to say this ATAS works as well as a large screwdriver antenna.  I will say that I am a "casual" mobile operator and for what I do with the mobile setup, I am quite pleased with the 857 and the way it works.  The display is smaller, but the color settings have quite a few more color choices.  I also have an FT-817 and the menus are quite similar.  

Just so you know I am not being partial to Yaesu I also own an IC-746 Pro.  It's perhaps the finest HF rig I have ever owned.  It doesn't have the menu system I had problems with.  It has KNOBS and SWITCHES.  

Good luck with your decision.

Differences of opinion are why we have horse races I suppose.  
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W4KVW
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« Reply #19 on: October 18, 2008, 01:20:46 PM »

I have ran 3 mobile HF setups with the following rigs & performances:ICOM 706 MII with DSP unit,YAESU 857D, & my current ICOM 7000 & BY FAR the 857D was the WORST I have EVER used or heard!I had noises that the DSP in the 857D would NOT eliminate no matter what.I used EACH rig in my shack as well & with the 857D I ALWAYS had an S-6 noise level on 6 meters in my shack but VERY little if ANY with the 706 MII,7000,or my base rig the ICOM 756 PROII.I did NOT keep the 857D very long since it made me ANGRY listeing to the EXCESSIVE noise on ALL BANDS while mobile.I used different antenna setups with each so that MAY have had SOME affect but I doubt very much.The ICOM 706 MII was used with a DK-3 Scredriver,the 857D was used with the ATAS-120A & the ICOM 7000 is used with Hustler antennas just FYI.ALL of them were used on the SAME antennas in my shack so that leads me to think the antennas were NOT the problem!I have owned & used MANY rigs in my almost 15 years of ham radio & I rate the 857D as the WORST HF rig I have EVER owned or operated.If I were offered another 857D for FREE & was told I had to use it to keep it I would DECLINE the offer even for FREE unless I could use it ONLY on our local 2 meter 440 repeaters which are VERY close to my location!In my case this rig is NOT impressive in ANY mode of operation due to the noise in it's reciever.

Clayton
W4KVW
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KF6HHH
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« Reply #20 on: October 18, 2008, 01:45:13 PM »

Thanks for the info.  I wonder if you may have had a bad one as several folks have said the 857 was a good radio?  I have the 897 and it does seem to be noisy, but I have nothing to compare it to and on the few occasions where I've been at other HF rigs it didn't seem to be too bad in comparison.  I had planned on the 706 but didn't know about the fan problems until this post, so not sure what to do.  I read about the IC 7000 and it seems like they don't have all the bugs worked out of it yet, so I'll just keep asking questions and trying to figure something out.
Thanks again,
Dan'o  :}
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W4KVW
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« Reply #21 on: October 18, 2008, 05:31:24 PM »

I also have owned an original 706 along with the 706 MII & NEVER had ANY problems with either.I never used the original 706 in a mobile setup so I did NOT use it to compare with the 857D.I have had ZERO issues as well with the 7000 & when it was in my shack next to my 756 PROII it was VERY close to being just as quiet as the PROII & the PROII is VERY quiet.I have a local ham friend here who uses the 897 & loves it but is considering selling it due to tales of MANY issues with Yaesu service that others are sharing with him including myself.I wanted too ship them the 857D & they advised me it would be 8 weeks at best before they could look at it.Sounds like they have LOTS of problem gear if they are backed up that far on repairs(This was about a year ago).I use the IC-7000 EVERY day in my mobile with ZERO issues & it is a GREAT deal on the used market at $1000.I traded my IC-746 PRO with a local ham for my IC-7000 & think BOTH are GREAT rigs! I just miss the 746 PRO in the shack now.Hope whatever rig you buy makes you happy since problem rigs are NOT much FUN to operate & ruin the FUN that they should bring from the hobby.

Clayton
W4KVW
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KF6HHH
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« Reply #22 on: October 18, 2008, 09:37:26 PM »

I figure it's like cars, everybodys had a lemon no matter what brand, or has heard about a lemon.  So I guess I'm looking for the consensus of opinion.  I'd love to have an IC-7000, but can't afford one and have heard bad things about them, but have also heard good.  I was told about the IC-706 back on the day I got my Tech lic, so I know it's been around a long time and is a good radio.  I've heard the FT-857 is just the mobile version of the FT-897, which most say is a great radio, so I guess I'll wait and see when I need to get the radio, then see how much the plastic can handle before it melts in the credit card slot (LOL).
Dan'o  :}
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N3OX
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« Reply #23 on: October 19, 2008, 10:29:12 PM »

The FT-857D's "slow" AGC is too fast.  Bothered me on SSB (in words, maybe: "harsh" or "fatiguing") until I soldered in an extra capacitor as per DG2IAQ's suggestion:

http://www.qth.at/dg2iaq/mods/DG2IAQ%20Modification%20Sheet%20--%20YAESU%20FT-897.zip

My '857D is, for now, my daily use radio and if I had problems on par with W4VKW's I'd go nuts.  The SSB thing was a bit annoying but I don't think it would bother me as much in a noisier background environment like a car.  Hard to say for sure.

73
Dan
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
AC7LY
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« Reply #24 on: October 21, 2008, 10:32:57 AM »

I am considering which of these two units to purchase as well. I am wondering which unit has the better separation kit? Especially in regards to cleanness of installation. Thanks

David
AC7LY
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N5IFH
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« Reply #25 on: October 27, 2008, 08:56:40 AM »

Just a suggestion...take a "serious" look at the IC-7000.
Hands down, a better mobile unit than the 706MKIIG or the 857 could ever be!

73,

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VE7REN
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« Reply #26 on: October 27, 2008, 10:11:30 AM »

ive had all versions of the 706,and currently own a ft857d.i am partial to icom,although the ft857d i did like prior to prchase,as i had gone and done the research. i really like the dsp up top,the colorful adjustments,home ch button,etc.i have done numerous a/b test with both radios on numerous antennas,and feel the 706mk2g outperforms the 857 in recieve and overall looks. the 857 has a horrible speaker with a not so loud output like the icom. the screen is a dirtrap {recessed }as compared to the 706.thew seperation kit on the 706 is much better built and looking in my opinion also. overall both are good rigs,but i will sell the 857d before the icom goes.
 ve7ren brent
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ZR1PJA
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« Reply #27 on: November 18, 2008, 01:59:57 PM »

While I agree that the IC-7000 is the better rig, I find it too much radio for mobile operations. It is fine for field stations and also base stations with limited space.
For mobile work I have used  both the IC-706 and the FT-857 and both are great. Even here, too much radio.

The only negative issue of Yaesu Rigs are the high costs of the accessories.
Brgds
Paul
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