The AM Forum

Hello. I recently got a Yaesu FT-857D ricebox for the car (currently my only shack), and while it is an excellent mobile rig for every mode other than AM, it seems to be even worse than most modern tranceivers when it comes to AM. At its default settings, the 25W carrier swings the meter downward with modulation and gets reports of low audio. Adjusting the carrier level downward via the service menu doesn't help. I can bring the carrier down, but the audio becomes more distorted. This technique may work with an 817, but doesn't work well with the 857 having a pa stage after. Being an obvious back burner afterthought, I believe the way that AM is generated iin the 857 is very inferior than other modern HF radios. Has anybody heard of anyone having any luck with AM tx in this radio? I am wondering if there is any mod floating around out there. Once I set up the base again I'll have other options, but this is all I have now.

SWR must be 1:1 and no more. The ALC will start to do the transient thing otherwise. A friend was on just last weekend with one of these on AM. They can work. Dunno what other problems might be happening.

I have a friend who bought the bigger boxed FT897 but essentially the same radio.
He said he found a switch on the back of the stock mic that switched mic response
between two different tonal qualities. He also said he found a menu setting that changed the
AM mic gain?
Anyway while he didn't sound like a high level modulated and modified AM transmitter would, he was certainly acceptable. At least to my standards.

Seems that all the Japanese rigs have 'downward modulation' but hey, don't let that stop you from
using it on AM.

Regards
Q

None of the Japanese rigs I have exhibit downward modulation.

Hi Steve,
Wonder what vintage rice boxes you have?
I have a TS 690 that does exhibit 'downward modulation' but my TS140 doesn't.
The radio club I hang out at has a TS690 also and a relativily new Yaesu that both
exhibit 'downward modulation'.
Thats why I had the thought that most do these days.

Regards
Q
 

Admittedly, mine are a little older, a FT-102 (mid 80's vintage) and FT-101 (70's vintage). The ALC is off in the AM mode in the 101. I've disconnected the ALC in the 102, although, even with it connected, I noticed little negative effects. Seems when the Jap rigs went to solid state finals, the ALC became more of an issue.

Have you noticed the downward modulation at all power levels? For example, even if you back the carrier power level down to say 10 watts versus the usual 20-30 watts, does the ALC cause problems? I'm wondering if it's a headroom problem or an ALC problem.

How about audio phase, try reversing the mike leads. SSB is positive modulation only.
See if you can disable the alc .

The problem is that the ALC is engaged in the AM mode.  One needs to disengage or disconnect the ALC in the AM Mode, to get proper positive peaks.   Even my FT990 exhibits  downward modulation, when the mic gain is et too high. 

One needs to turn off the ALC in AM.  The positive peaks drives the ALC into action, dynamically reducing the output during audio peaks.

Turning off ALC isn't an appliance option. One needs a screwdriver, solder iron and some idea what he/she is doing.
Maybe there is a rig which allows this in a menu but it's doubtful.

We actually talked about this type of thing last year. Bacon called it "reverse carrier control". Using the Search function here, I found the thread:

http://amfone.net/Amforum/index.php?topic=6429.0

...I HAVE AN FT847...NICE LITTLE RIG, RECEIVE IS GREAT ON ALL MODES, BUT SUCKS ON AM...I'VE TRIED MANY THINGS FER IT, BUT NO LUCK...BUT I HAVE HERD GUYS WHO SOUND OK, MINE JUST SOUNDS LIKE GARBAGE..I GUESS SOME GUYS MUST BE LUCKY IF THEY GET ONE THAT SOUNDS GUD ON TX...MINE ALSO HAS A VERY QUIET MONITOR CIRCUIT...OTHER GUYS HAVE SET THEIR MONITOR AUDIO TO A LOW LEVEL, WHEREAS MINE IS WIDE OPEN, AND STILL NOT GUD ENUFF...TIM...SK..

Hi,
Thanks for all the comments. I restored the default values and then backed down the carrier only slightly. It isn't great but it works and functionally qualifies the radio as an all-mode. It really doesn't sound too terrible other than that, yes, ALC is a bit too restrictive. I may look into loosening it up. A compact radio as the FT-857 doesn't have a dedicated AM tx stage. FYI from the tech liiterature:
"AM Modulator Circuit"
"As in the SSB modulator circuit, a carrier signal appropriate to the transmitting mode (AM) from the CAR-DDS unit and an audio signal from the microphone are applied to the balanced modulator Q1071 (SA602AD). The control signal from the mode switch IC causes a voltage (AM 5V) to be sent from the transistor via D1059 (BAS316), causing the balanced modulator to lose balance. The restored carrier signal and modulated signal are then fed to the TX mixer via the ceramic filter."
That's what I meant in my original post about the "inferior" way the AM is produced.
I'll live with this now and next year the base will have my Kenwood and hopefully I can pick up a nice vintage rig for great AM.
73
N2JKV

On all current model rice-boxes, a high modulation  (mic gain) level will drive the ALC into action. I've found that backing off the mic gain will prevent excessive ALC action, while retaining decent mod %.  Try that.

There's nothing at all inferior about that type of modulation.  Done correctly, it can provide absolutely superb audio.  The only hitch in the gitalong here is that the AM signal goes thru the ceramic filter, and the audio circuity prolly shapes the bandpass for 300-3000 hz.

I've modified several junk Heathkit slopbucket rigs for hifi AM using the existing balanced mudulator.  Works FB with a bit of audio work, and bypassing the crapstal filter!

Bingo dude!

See here.

http://www.amwindow.org/tech/htm/602mod.htm


and here


http://amfone.net/Amforum/index.php?topic=4888.msg36657#msg36657

That is very true about the both the FT-857,and the FT-897.  I have an 897 (I'm broker than broke, so I'm stuck with it for now). Both rigs have separate mike gains for each mode.  The gain goes from 0 to 100. The factory default is 50. Every comment I've read about these rigs, and my own experience tells me that the the factory default value of 50 is overkill for SSB, FM, Digital modes (which are SSB based), and more than likely AM.  Yaesu gave these rigs excessive mic gain.  In my experience, a good starting point for the mic gain is around 20-22.  Numerically this seems low, but much more than this, and the audio in every voice mode gets downright nasty.  BTW, the switch on the back of the mic, is basically just for a capacitor.  From what I've been told in on-the-air tests on 2m SSB, Position 2 just adds more bass.  Yaesu has made hand mics with this option for ages.  I used to have an FT-736R in the 90s (good rig - I used it for weak signal stuff on 2, 222, 432, and 1296 - wish I didn't have to sell it), and it's hand mic had the same switch, and it did the same thing.  Now if I could just scare up a QSO or two with my 20-25W of carrier, pee-wee signal (running 100W or more of carrier from an apartment is just asking for trouble with my neighbors).

73,
Ellen - AF9J

 .

I hear a  lot of solid state transceivers with good audio on AM.  Never paid much attention to what brand appliance it was.  The best sounding ones seem to mostly be Icoms, IIRC.  But since the band expansion I have heard a lot of guys try out their stock rigs on AM and answer my CQ's in the Extra class segment, where the congestion is still low. I have heard my share of lousy audio from those rigs, but a few could have told me they were running a converted broadcast transmitter and I would have believed them.

DG2IAQ has a list of modifications to the FT-897 that may well apply to the '857 as well. IN that list, there is a discussion about audio pumping by the ALC circuit. The suggested correction is to add additional capacitance to the ALC time constant circuit to slightly delay its response to audio peaks.

What I found to help the AM audio on the Yaesu FT-857D: first go to the alignment menu and turn the output power wide open - both AM carrier and and SSB. Next you go through the alignment menu and there is a setting for the ALC - turn it down about half way. Next, turn the power down to 80 by the main menu. I also find that when you use the LPF, and also use the #2 setting on the mic and turn the processor on to about 30, that it really improves the AM audio.

I have been told that it sounded pretty decent when I tried it on 75m AM.
My next step is to get the SSB filter for it, since it can be used on TX, and see what it sounds like after I install it.

John G., KC8NTP, east central Nevada

            "My next step is to get the SSB filter for it, since it can be used on TX, and see what it sounds like after I install it.'

I would venture a guess that any added ssb filter is more likely to reduce the audio quality of the transmitter by reducing the available bandwith.  .......  anyway, "try it, you'll like it "....       klc

On my Icom 718, you have to turn the mike compression off, and back down the mike gain until the output power stops dropping on audio peaks.   Its not my regular AM rig, but when I do use it on AM most people comment that the audio sounds good, although never fully modulated.

 I take a different approach on my 718-  Mic gain around 10 with the compression on.  Gives the audio much more presence and is not objectionable with a D-104 on which I changed the element with a Radio Shack condenser, and with the Heil ICM.  It's the only rig I have for AM, and seems to be doing very well at 25W carrier, sometimes into the SB-200.
 

  Rick

 W4FCC

Nice call Rick ;)

Rick-  I'll try using the compressor and backing down the gain more.    Looks like you got the call before Riley had a chance at it.

Riley... ha!
Thanks-- I had to wait out the post-Katrina freeze, took nearly 4 months.

  Rick

 W4FCC

There's a Ham feller in this forum, W2VW, who modified my TS440 and it gets great audio reports. The ceramic filter was subbed for one with lot more BW and the ALC was disabled. I have to make sure that the Tx is operating in a very low SWR. Im sure there were other things done, and I'm very happy with the results.
As the others have responded, there are rigs out there that have excellent audio without any mods.
G'day
Fred

This isn't the hardest, but not the easiest.

Yahoo uses a NEGATIVE going ALC voltage, so you have to put -4 to 0 volts on the tip of the ALC plug.

Go into the menu system, change the AM carrier control to 100 percent (100 watts), then take a resistor / pot divider, and put from 0 to -4 volts on the 1/8 stereo mini-plug, using the voltage to set the carrier power.

This will allow the radio to use the ALC to set the CARRIER power, but since you have an external ALC voltage, it won't continue to act and clip the audio power.

Sounds as good as any other low level modulated radio out there.  W8JI has instructions on his website, and I think others have talked about it here.  With a D104 on my FT-857 I get good audio reports.

--Shane
KD6VXI

I messed around with my 897D (exact same PA and RCV boards as the 857 series) and found that the service menu adjustment for the ALC is a very clean way to delay the early onset of ALC intervention. John (KC8NTP) also mentions this earlier in the thread. Obviously, it is wise to save all your factory service menu settings before you make any changes as each rig has its own unique settings. If your 817-857-897 is connected to your computer, there is a free program called "Modify" that allows you to export all your Service Menu settings to a file. It's still floating around on the internet, but if someone can't find it and wants a copy, I have it here. If you mess things up, you can import that file with all your factory settings back into the radio. The program will also allow you to change Service Menu settings on the fly.

If you don't want to mess around with the Service Menu, the external ALC setup mentioned by Shane works very well with these rigs. I built one for my 897D to keep it out of ALC when using it for the digital modes, but it works great on AM as well when you set the rig up as Shane described.

The biggest problem with using the 857/897 rigs on AM is that Yaesu runs the AM signal through the 2.6kc sideband filter, allowing a maximum bandwidth of 5.2kc. I grabbed a plastic ceramic 10kc Murata filter that I had left over from an old 10 meter FM project, and installed it in one of the optional filter slots. It produced a DSB signal that was close to 20 kc wide (sounded great) while operating either upper or lower sideband, but unfortunately, you cannot select either of the optional filter slots for TX in AM mode. The only way around it would be to bypass the CFJ455K filter during TX with a cap. That would not be difficult at all, but by the time I figured this out, I had several other rigs for use on AM, so it became pointless. I ended up abandoning the project and restoring everything back to stock.

I find that the only way to get decent AM on my ICOM-706MKIIG is to turn off the compressor and back the mike gain down to a "3" out of a max of 10. Setting the output power from 15 to 20 Watts gets me 375-400  Watts of power out of my Henry 2K4 so I'm happy.

That will have to do until I get my SHAFTT exciter completed.

Phil - AC0OB

AEX,

LOVE that modify program.  MUCH better than having to blow down a complete memory map after screwing with service menu settings each time!  Saves the EEPROM, I'm sure.

I'd be interested in any other notes you have on the 897 / 857.  I love mine, ham radio deluxe makes it usable :/

Also, the ALC trick makes ALC overshoot a thing of the past... AND you can use it as an external Pout control....  Easier than menu tweakin'.

--Shane
KD6VXI

Sounded fine here in NJ if that's what you were on with last evening.

Shane,

Yah, it's an amazing little 160 meter - 440 MHz station that's smaller than the lunchbox I used to carry to school when I was a little squirt. DG2IAQ (Jochen) compiled many notes on the 857/897 radios and very nicely documented them in PDF files. He has them all stored on his smartdrive which is linked to this address:

http://www.qth.at/dg2iaq/mods.htm

Jochen's squelch modification works very well and only takes a few minutes to do. It's well worth doing if you use the rig to scan the VHF air band or the FM modes on VHF-UHF. My notes are primarily about all the issues dealing with incorrect bias settings in the pre-driver, driver, exciter, and PA stages. This caused all kinds of issues with 857/897 rigs manufactured between 2004 - 2007. All that stuff is here:

http://members.cox.net/w1aex/897idle.html

It's a great little radio and very rugged.

Rob W1AEX

Well thank you. I think we have found the sweet spot for AM operation.

Phil - AC0OB

I have been doing some reading on this tread, and would like to know if anyone can give me a link to the free program called "Modify"?  I have done some searching, but have not had any luck.  Any help would be great.  I have a NEW FT-857D, and would like to get it sounding the best I can.

Thank you for your time, 73's
-scott

Me too!! I looked for the program but couldn't find it.

Aha, looked at the screen shot and the web site is at the bottom. Just went there and downloaded it.  ;D

http://www.dl4cu.de/

I use modify myself...  If you guys have trouble getting it, I'll send it via email.  Very small, and GREAT for making modifications on the fly.  You can also use it to download a complete copy of the memory map.  Recommended for use on all the newer menu driven Yahoo rigs.

I've been using the 857 on AM for a couple days now...  Decent rig, surprises most people on AMI-West Coast..  15 watts of carrier at 6K feet does wonders.  As long as you KEEP the ALC meter from moving at ALL under full modulation, it really is a decent sounding radio.  Not a wideband Class E, but capable.

--Shane
KD6VXI

I looked at that site myself, and found this on there on the download page. " Modify-function does not work with FT857D and FT897D !!!!! "

Have you tried it on a FT-857D yet?  My radio is less then a week old.  I am not sure that download right yet myself.

Are you using that program on a ft-857d?  And if so and it works, I would like a copy please. And any extra info I can get would be great!  Thank you.

I'm using it to modify my menu programs.

I've 'hard modified' the rig for all band xmit.

I <<believe>> the only thing that doesn't work is the 'softmod' version on modify, which would allow you to modify the radio for full tx, without doing any jumpers.  I've jumpered mine.

OTHERWISE, I've found NO problems using MODIFY.exe on a 857D.  Yes, D model.  I have DSP built in. (just trying to make it as clear as possible)...  Not added, it's factory (my radio came with 60 meters factory).

--Shane
KD6VXI

GREAT!  My FT-857D is about a week old, it has the factory DSP, and 60M band.  I bought it through HRO.  If you can Email me the program you have that would be great. 

My mail is:  kd8piq@arrl.net

Thank you for your time!  73's