14Oct00

Headphone Volume

A number of postings have commented that the headphone audio is very low compared to the speaker. This is particularly true with a popular set of headphones, Heil Proset. As a result, settings like monitor volume and sidetone, which are independent of the AF control (i.e., they can only be set on the menus) are out of whack depending on whether you're using the speaker or headphones.

In looking at the schematic (may not appear in your Operating Manual's schematic), one sees that Yaesu shunted both the L and R legs of the headphone audio to ground through 2.2 ohm resistors. In conjunction with the 100 ohm resistors, they form a voltage divider. These 2.2 ohm resistors appear to have been added during production as an afterthought. They have the effect of substantially reducing the headphone audio. These resistors are mounted on a little circuit board which is just behind the headphone jack on the rig. If you remove these 2.2 ohm resistors, the audio level will come up substantially, too high, I thought.

If you replace those 2.2 ohm resistors with 10 ohm resistors, the levels are much closer between speaker and 'phones. This was for Heil Proset 'phones. In later production runs, the tacked-in-place resistors have been replaced with chip resistors, making it a little more challenging to replace them.

One poster commented that he replaced the 100 ohm resistors that are in series with the L and R outputs with 10 ohm ones, and that made it satisfactory for him. Other postings (June 99) suggest that you can experiment with a wide variety of swaps. One suggestion was to replace the two 100 ohm resistors with either 22 ohm or 10 ohm ones (leaving the harder-to-reach 2.2 ohm ones alone).

Another posting suggested that using an external speaker with a phone jack and volume control solved all the problems and didn't involve surgery on the radio. This suggestion makes a lot of sense.

Keep in mind that the proper resistor values will depend on which brand of 'phones you're using, so you will have to experiment. Too bad there weren't pots for this setting.

To get at the headphone circuit board, you must first remove the two case halves (eight screws). Then remove the top screw on each side holding the front panel to the chassis. Now loosen, but don't remove, the two lower screws. This will allow you to drop the front panel down and you can see the little circuit board for the headphones. It doesn't appear too easy to remove this board for ease of working on it.

Update 11Mar00: Click here to read how to disassemble your rig's front panel. After removing just the black plastic facepiece, you can then remove the headphone jack completely to work on it. If you don't disassemble part of the front panel, you will not be able to remove the phone jack.


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CTCSS Issues

On earlier models (at least), the CTCSS decode function does not work as intended. First, the radio "falses," or opens the squelch even though a valid CTCSS tone was not received. You can check this out yourself by tuning to an FM frequency, and then turning on CTCSS Decode by pressing TONE twice. Leave the squelch knob fully counter-clockwise. You should hear no white noise at all, but may find that occasionally you'll hear bursts of noise. (Note: This was a problem on my FT-50R until I installed a factory upgrade changing a couple of capacitors and a resistor.)

Another problem is associated with CTCSS tone 118.8. Sometimes the radio will not decode this tone even if a valid tone is present.

Yaesu tech support advised me that this has been fixed in later models, but a recent posting said that the problem with falsing was still present in a 8K15 version.

Workaround: Don't leave your squelch fully open. There's no need to anyway. A squelched channel will stay silent and will only open on the proper CTCSS tone.

Another anomaly: The value that you have in Menu #12 TONE-FRQ does not necessarily stay where you set it to. If you tune to a memory channel that has a CTCSS tone associated with it, then Menu #12 TONE-FRQ will then hold that value, not the one you originally set. Think of this menu setting as the place where you tell the radio the CTCSS value you want to put into a memory channel. Some people have been confused by this behavior.

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Fixes by Yaesu under warranty

When Yaesu upgraded the CPU in the radio in later production runs (to do bi-directional CAT operations on frequency and mode), it offered to upgrade any earlier rig that lacked this feature and was still under warranty, and performed this service for what seems like a large number of owners. In fact, Yaesu USA has performed in an exemplary fashion in taking care of the concerns of nearly all owners with problems.

Depending on the version of your radio (see how to tell here), if it's still under warranty, then Yaesu will repair and upgrade to the current version. Be sure to tell them the specific things you want modified under warranty.

If you're in the US, you do not need to advise them that your radio is coming. Just be sure to package it well (double boxing with plenty of protection), put in instructions for what you want them to do, and send it to Yaesu USA, 17210 Edwards Road, Cerritos, CA 90703. They will fix it and return it to you in the box you used to send it to them.

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Fixes not entertained by Yaesu

People have asked Yaesu to "fix" the volume control problem, but the company has stated that it does not consider it to be a problem. Later production runs seem to have gotten the CPU programmed better and this is no longer reported to be an issue in recent postings.

Yaesu has also announced that there are no plans to modify the radio so the FC-20 auto tuner and CAT control can work at the same time.

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Volume Control Issues

The volume control is a pot that provides input to the front panel CPU. Thus, the actual audio output is dependent on what is programmed into the CPU rather than directly from the pot setting. The result of a likely design error in the front panel CPU is that no audio is audible until the knob is turned up to a position somewhere between 0800 and 0900. At that point, the sound comes to life. Some people have complained that when it comes on, the level is too loud for comfortable use. Others see this as a design quirk and live with it.

It appears Yaesu does not consider this a warranty item (maybe they did some fixes on early models?). Some have suggested some minor surgery consisting of cutting pin 1 of the audio IC and soldering in a resistor between the two pin ends. This has the effect of reducing the audio output overall, so that when the audio does come on, it is not as loud, but does not really fix the problem.

Yaesu appears to have made some changes in this circuitry or firmware during later production runs, and recent (5/99) reports on the bulletin board suggest that the problem is now non-existent or minimal.

Update 14Oct00: I had a discussion with Mike N6MIK at Yaesu USA, who said there is no new mod for the volume control issue. The fix that Yaesu talks about is one that corrects a major volume control problem that existed on very early models of the FT-847. Mike said that by production run 03 or 04 (i.e., xx03xxxx, or xx04xxxx), they had corrected the problem, from their perspective. This is NOT the same as the issue a number of folks have brought up, that of a dead spot at the beginning of the rotation and then the rig's audio coming on too strong. Yaesu does not consider this a problem or, at least, does not have any fix for that behavior.


Portions of a posting I made to the bulletin board are reproduced here, for any use it may have.

If your rig is from a production run later than 3rd, then you have the current "fix" and there is nothing beyond that. Even if you have one of the early models, if it was returned to Yaesu for the "bidirectional frequency/mode upgrade," it likely has the volume control update as well. In understand both fixes involved firmware upgrades.

You can hear this digital method yourself if you put your radio on white noise and slowly turn the volume control up. You will first notice a "dead spot" where nothing happens, and then you can hear the changes in volume, in discrete steps. On my radio, the first level is at 0800 "clock time," the second at 0815, third at 0830, etc. By 1000, I can discern 10 different levels. Beyond that, the sound is so loud I can't discern the changes.

Some people have done a fix by soldering a resistor in one leg of the audio amp. This involves cutting one leg of the chip, in place, to put a resistor in series with that leg. Others have used external speakers with or without volume controls. Most recently, a low resistance in the line to an external speaker seems to have worked quite well. The rig has so much audio, you can tone it down with a resistor and there's still plenty. However, none of these fixes change the basic way the volume control operates.

The radio is complex, and getting the correct audio levels is also complex. For example, the audio settings that you can change from the menu are generally independent of the volume control setting, so they may not always be at the desired level, depending on how, and with what, you are listening to the audio. Also, the headphone jack is specified for 16-32 ohms, so other impedance headphones will be either too loud or too soft. The FAQ discuss changing resistors in the network for the phone jack, to adjust the levels for your particular phones. Others use an external speaker with an adjustable headphone jack.

Some people find the volume control objectionable, while others seem to have other competing noises (e.g., rig fans, computer fans, etc.) so the behavior is not objectionable. The bottom line, I think, is that the rig is sound and cannot be everything for everyone. There are "unique" aspects of the rig, but many workarounds for the resourceful.

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DSP, General

The FT-847 has an advanced DSP, featuring a digital filter, digital notch, and digital noise reduction. These are implemented in the audio stages of the rig. Generally, DSP can be implemented in the IF stages or audio stages. Because this rig uses the audio stages, there are some hints that you will need to know about to make the best use of the digital signal processor.

The digital operations are based on microprocessor manipulation of the audio spectrum of a received signal. Please note that the three DSP features are complex and require some knowledge and operating aspects to make the best use of them.

If you have access to an audio spectrum analyzer program, such as the excellent freeware program, Spectrogram, by Richard Horne, you can learn a lot about how the digital operations work on the received signal. It is worth getting this program for this purpose as well as a number of others.

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Digital Notch Filter

The notch filter part of the DSP works very well at removing annoying heterodynes from the portion of the audio passband that you're listening to. It's capable of identifying multiple heterodynes and other noises with the bandpass of the filters and of squelching them out. It's uncanny to listen to it; it takes about a second for it to find them and reduce them to virtually inaudible. Of course, if you're trying to listen to CW, you can't use this feature, since it will eliminate the signal you're trying to listen to! The filter is most useful when listenting to complex waveforms such as speech.

I have found some complex whistles that the notch filter will not remove, presumably because they are complex and not simple frequencies which are the target of the algorithm.

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DSP Digital Filter

On SSB, the digital filter allows you to use two counter-rotating knobs to reduce the audio bandwidth from the high end and low end. There's a Low Cut knob and High Cut knob, and they work as expected. The action of the knobs is quick, and you should become used to moving them just a little at a time. Because the system is digital, you can sometimes hear the different levels of filtering as they are switched in while rotating the knob. This has led some to complain that the filter sounds like a dirty audio pot. See the discussion by clicking here.

On CW, the digital filter operates in a different fashion. In the CW mode, the digital filter operates in a bandpass mode, with bandpasses of 25, 100, 200, and 400 Hz. The Low Cut and High Cut knobs are non-functional when in CW mode. By changing Menu #10 CW-BPF, you can vary the bandpass between the four values. It's extremely efficient, too. Just tune in a CW signal and try the various bandpass settings to see what effect they have on the signal. I am amazed at how well it will kill signals outside the bandpass selected in Menu #10 CW-BPF.

Because the DSP is in the audio circuitry, it can be affected by strong adjacent signals in the IF, and their effect, in turn, on the AGC circuitry. See a discussion of the effects of strong signals under Filters. Also, the review of the Collins 300 Hz mechanical filter includes a lengthy discussion of "AGC pumping." Click here to go to that review if you would like to read it.

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Clicking sound heard on DSP

Some people have commented that when they rotate the Low Cut and High Cut DSP knobs on SSB, they can hear a clicking noise in the speaker. Some likened it to a dirty pot sound. The problem seems to be more pronounced when listening to non-voice signals, and it appears to be due to the digital nature of the knob adjustments (i.e., the knobs are providing input to the DSP CPU rather than directly adjusting a circuit). The clicks are more pronounced when turning the knobs faster. The clicks appear to be a result of the design of the radio and not a symptom of something wrong with one's radio.

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Noise Reduction DSP

The noise reduction feature of the FT-847 attempts to balance the ability to preserve a received signal with a reduction in otherwise undesirable noise. It is not a general noise reducer, as you might expect, but a sophisticated signal processor. If you use a spectrum analyzer program on PSK31 signals, for example, you can easily see how the NR DSP will reduce surrounding noise while leaving the desired signals so you can detect them. The company has not released detailed information about the NR feature, but it is clearly a complex piece of firmware.

Some people have been disappointed in the NR DSP because they expected that it would quench overall background noise or hiss to make general listening easier. For people on VHF/UHF looking for weak signals, it is common to leave the internal pre-amp turned on. If you try to use the NR DSP on a no-signal portion of the band, in time the NR DSP will allow the overall noise levels to rise to nearly what they would be without a signal present. Perhaps it's searching for a phantom signal? The company discusses NR DSP in the owner's manual and notes that, levels of background noise high enough to generate any reading on the S-meter should be reduced so the NR DSP can do its thing. See page 38 in the manual for more information on how to optimize the NR DSP.

I have also found that sometimes the NR DSP seems to get "tricked," particularly if you change RF gain or turn a pre-amp on or off after turning on the NR DSP. I have found that the best way to use it is to, first follow the directions on p. 38 in the manual to adjust gain, and then to turn NR DSP off and back on after you have done the adjustments to the RF gain or pre-amp.

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Filters

The FT-847 comes with two discrete IF filters and has a slot for a third one for CW. The two that come with the radio are ceramic filters and there is one for RX and one for TX. If you don't add an optional CW filter (and then select the NARrow button), the RX ceramic filter is used for CW. Yaesu sells three optional filter for this radio and INRAD sells a number of them for the FT-847 (and many other radios).

The selectivity of the FT-847 on HF is acknowledged to be suitable for "casual listening" on HF. You can read a review on a 300 Hz. Collins Mechanical CW filter for the FT-847, but here are the essentials you need to know about:

The IF bandwidth of the rig with the stock filters is wide enough that the rig hears the signal you are centered on plus nearby signals that you might or might not hear. You can use the DSP and the IF shift to suppress those unwanted adjacent signals, and the DSP works superbly well for that purpose.

However, those adjacent signals, even if you can't hear them (because you've got your DSP on), can still affect the signal that you are listening to. Since those adjacent signals are getting into the IF, they affect the AGC control of your radio. If the adjacent signals are strong enough, then the AGC will activate and will reduce the strength of the signal passed to the audio circuitry (and the DSP). Thus, the signal you want to listen to will be suppressed as well, sometimes to the point of being inaudible. This action is called "AGC pumping." Since you can't turn off the AGC on the FT-847, you're stuck.

By using supplemental filters designed to further restrict the IF bandwidth, you will suppress the adjacent signals much more deeply than the stock ceramic filters, and the AGC action will be substantially reduced. Radios much more expensive than the FT-847 tend to have better filters built in; it's really a case of paying for what you get.

Yaesu sells the Collins (R) mechanical filters for the FT-847. There is a 500 Hz CW filter, a 2.5 kHz SSB filter, and a 6 kHz AM filter. International Radio, or INRAD, sells both Collins mechanical filters and crystal filters for the FT-847 and many other amateur radios. Click here to read some more about INRAD's products.

Update 08Jun00: The CW filter uses a different form factor for the plug-in board from the SSB filters. The two SSB filters, however, are identical in form factor. So, you can't just swap a CW filter into the SSB slots without changing the board to which they're attached.

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INRAD Filters

A number of posters have commented on the helpful service from this company. It's a small operation in Oregon which sells both the Collins mechanical filters and multi-pole crystal filters for a wide variety of brands of amateur radios. Their prices are generally less than the major vendors charge for the Yaesu options. Their web page now contains actual filter shape curves for many of their filters. The "newsletter" is an excellent tutorial on IF filtering. They can be reached on the web at http://www.qth.com/INRAD. The crystal filters for the FT-847 are $150 each and the Collins mechanical filters are $120 each.

Chuck KE3KR installed three INRAD filters, and his comments are included here because they are highly informative:

"OK, the INRAD filters arrived today and they're now installed. I'm using the 2.6 kHz mechanical filter on SSB TX, the 2.1 kHz crystal filter on SSB RX, and the 250 HZ crystal filter for CW RX.

"The change to the receiver performance is simply phenomenal. I'd recommend this setup to anyone. SSB is no longer fatiguing to listen to. CW is unreal, especially when I can cascade a 25 Hz DSP filter behind the 250 Hz crystal one. I haven't gotten a TX signal report yet, but the TX audio should be improved with the mechanical filter replacing the ceramic one. The RF speech processing works great. I'm limited to 50W until I receive the Yaesu PS I ordered, but even before installing the new TX filter I managed to work KG4AS from Guantanamo Bay on 20m in a pileup. I also hear very little ringing from the 250 Hz CW filter.

"Installation was surprisingly easy, though tight. I unplugged the 3 coax cables (L to R, viewed from bottom, color coded yellow, none, brown) coming from the front of the circuit board, and also the plug at position J1004, so I'd have room to route the coax from the filters under the existing cable bundle. After installing the filters, I also had to spread that large cable bundle around one of the IF transformer cans on the circuit board to be able to comfortably fit the case bottom back on. BTW, this data is from a 9G serial number; your color codes may vary. All I can say is, wow."


20Jan00 Update: The following text is taken from the Inrad catalog (which is an excellent tutorial on filters) and may help someone decide whether to get the 1.8 kHz crystal filter or the 2.1 kHz filter.

"The 2.4 kHz filters are used to improve selectivity in radios which are normally supplied with a 2.7 kHz filter. The improvement is modest, but it is noticeable and fidelity is compromised little.

"For most general operating conditions, the 2.1 kHz bandwidth is ideal. It is the best compromise between intelligiblity and qrm reduction. It's a good bandwidth for dxing and contesting as well as rag chewing in crowded bands. The 1.8 kHz filters are most useful for contesting where conditions are severe."

08 October 2002 Update:
Barry W4WB sent in a photo which shows you how to properly route the cables, etc. for the installation of the INRAD filters. You can take a look at the photo >> here << !

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Voice synthesizer (FVS-1A)

One option for the radio is the FVS-1A voice synthesizer. This unit, intended for use by the visually impaired, speaks the frequency and mode when the Voice button is pressed on the front panel.

Installing the FVS-1A. To install this unit, first remove the eight screws holding the top and bottom covers on. Remove the two covers. Then, remove the top two screws (one in each side of the radio) that hold the front panel assembly to the radio. Loosen, but don't remove, the two bottom screws. Now you can drop down the front panel and expose the back of it.

On the FVS-1A, you must set English or Japanese as the language, then plug the attached cable into the multi-pin jack on the back of the front panel. Finally, use the double-sided tape to fix the FVS-1A to the back of the front panel. Reassemble everything. Some commenters have said the audio output from the FVS-1A is too low. There does not appear to be any way to boost the audio output from the unit, however.

Update: Rob KF2EK reported that there is a variable resistor on the FVS-1A board for setting audio level. He turned his rig on with the front panel dropped down and tweaked that pot until he got the loudest possible sound (still not booming, but an improvement over how it was shipped). He said it was the only pot on the circuit board.

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Service Manual.

The Technical Supplement, or service manual, is an option. You can purchase it from HRO for about $28, and presumably from other ham stores or from Yaesu directly. For your money, you will get a package of looseleaf sheets for which you will need to provide a binder. The manual consists of a half-page introduction, a tutorial on replacing surface mount components, an alignment section, a block diagram of the radio, schematics for each version of each circuit board, and complete parts lists with the version identified for each part.

Alas, there is nothing in the manual regarding the design and functioning of the rig. The alignment section gives the methods of doing an alignment of the FT-847. You will need the usual lab equipment to do an alignment, ranging from DVMs, RF and AF signal generators, frequency counters, wattmeters, linear detector, RF attenuator, and a Spectrum analyzer good to 1 Ghz. (Well, I have not yet found a reference in the service manual to needing a spectrum analyzer at all.)

Once you have the necessary tools, alignment (click here to read about the hidden alignment menu) generally consists of injecting a signal in a port and then either adjusting pots (there are diagrams pointing them out) or front panel settings, and then memorizing the settings with a front panel button. The schematics and parts lists have a very helpful feature; for each schematic and part, the production run is identified. There are a number of schematics for some circuit boards to show the various changes in them.

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ATAS-100

The ATAS-100 is a motorized vertical antenna for the FT-847 and FT-100 radios. It covers the 40m through 440 bands. It is intended to be used mobile, or can be used for a fixed station with an appropriate ground. Yaesu sells a kit, the ATBK-100, for those wanting to use the ATAS-100 at home. For a while Yaesu was giving the ATAS-100 away free when you purchased your FT-847, but they appear to have ended that offer.

The two radios that support the ATAS-100 send a DC voltage on the coax to cause the antenna to grow longer or shorter, depending on the band you're tuning for. You can't use the FC-20 Autotuner and the ATAS-100 at the same time. Of course, you do not need both.

The use of the antenna is covered on p. 62 in the owner's manual for the FT-847. In it they discuss the possible need to adjust the length of your coax (to "eliminate the possibility of adverse transformer action in the 50 ohm cable"!). Some people have reported that the ATAS-100 is confusing to operate because the radio causes the antenna to retract all the way and then tunes by lengthening the antenna (or vice-versa). If you watch the antenna while letting the FT-847 tune it, its actions will make more sense. Better yet, take a look at the reviews section of this site for Len K1LU's discussion of the ATAS-100 system. See also the discussion on Antenna Connections and Duplexers.

Gerald AC5OG built a autotuner between an ICOM 706 and the ATAS-100. He reports that +8.5V applied to the coax causes the ATAS-100 to retract, and +13.8V causes it to extend. So, the FT-847 in the tune mode detects an SWR that's too high and commands the ATAS-100 up or down by varying the voltage.

Update: Some people have reported receiving error messages on 160m and 80m (one also said 40m) when trying to transmit within band. Although the cause of the error messages is not yet clear, they do seem to be related to the use of the Menu #31 setting of "Ant" instead of "Tuner." The Antenna setting implies that the ATAS-100 antenna is in use. This antenna does not support 160m and 80m, so these error messages might be related to the ATAS-100. I add this just so you can track down similar error messages.

Update: A ham (who will remain unidentified) reports that he smoked his ATAS circuitry in the FT-847 after he removed the ATAS-100 antenna and put a wattmeter in line that had a DC ground on the coax. He was sure he switched the Menu #31 setting back to Tuner before removing the ATAS-100, and turned the radio back on. After a little while, smoke came out the back of the rig and the ATAS no longer worked. The same ham reports that the ATAS-100 instructions caution against allowing a DC ground to exist when in the Ant setting (instead of Tuner) of Menu #31. I could find no warning about this in the Operating Manual for the FT-847. A word to the wise. Note that this is a separate issue from turning on the mast-mounted preamps in Menus #29 and #30; on these the manual is clear not to present a DC ground to the rig's jacks.

Update 21Feb00: Lee Devlin, K0LEE, has implemented a FT-100 FAQs page which contains additional information on installing and using the ATAS-100 motorized antenna.

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ATAS-100 Menu 31 Setting Reverts to TUNER setting

A recent (June 1999) posting said that the user pressed the TUNER button to activate the ATAS-100 antenna but found that 1) the tuner icon didn't light up, 2) he heard a double-beep, and 3) The Menu #31 TUNER setting had reverted to "Tuner" from "Ant." It did this repeatedly; switch Menu #31 back to Ant and the same pattern would repeat.

Two postings followed. In one case, the person said the same thing happened to him and he cured it by grounding his ATAS-100 "more." In the second case, the user had a triplexer that went bad. Replacing that cured the problem.

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Radio Hangs Up in TUNER Mode

If you change Menu #31 TUNER to "Ant" and press the TUNER button, but don't have the ATAS-100 antenna connected, you will hang up the radio in the tuner mode, trying to tune. I got it to go away finally by pressing the TUNER button and waiting for a couple of minutes. I think the WAIT icon was lit up. Then (and only then), you can go back and set Menu #31 to "Tuner" and get back to business! Otherwise, it's the dreaded RESET since powering off doesn't seem to release it.

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