21Mar01

Satellites - General

For many people (including me), buying the FT-847 opened up the world of amateur satellites for them. There are some interesting features of satellite operations that some posters do not seem to be familiar with.

Satellite operation in full duplex means that one is simultaneously transmitting on one frequency and listening on another band to the signal coming back from the satellite. Doing this brings with it issues that don't arise during normal operations on HF and FM. There have been many postings on the web page about "problems" when operating in the satellite mode, but many of them appear to be normal duplex operations and a lack of familiarity with them.

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Speech Processing in Satellite Mode

The schematic for the FT-847 shows that during transmit the signal is routed through the TX filter AND through the RX filter when speech processing is turned on. This helps in shaping the outgoing signal and to keep it within the proper bandwidth. When operating full duplex in the satellite mode, simultaneous receiving and transmitting is occurring, and the receive and transmit signals are processed through their respective filters. This is the reason you can't use the speech processor when in full duplex satellite mode on the FT-847.

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Desense problems in Mode J

When operating full duplex in the satellite mode, you are receiving and transmitting simultaneously. Mode J uses a 2 meter uplink (transmit) and a 70 cm downlink (receive). The third harmonic of a 2 meter signal falls in the 70 cm band. Even though the harmonics are surpressed, enough energy gets out and is captured by the receive antenna to overwhelm the signal coming down on 70 cm from the satellite. You can hear this on your radio when tuned to certain frequencies as a distortion of your transmitted signal. There is no delay and that's how you can tell it's not coming back from the satellite.

This is a relatively common problem in Mode J. About the only cures for this are to either separate your antennas substantially, add a bandpass filter on 2m, or to construct a cavity filter for 70 cm that will null out the interfering harmonic.

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Crossband operation in Satellite Mode

When in satellite mode, you cannot transmit and receive on the same band in duplex; you must use two different bands. This is different from running in the split mode (non-satellite mode), where you can receive on one frequency on a band and transmit on another (but not simultaneously like in the satellite mode). Also, you cannot use repeater offsets when in the satellite mode (which you have to be in order to turn on the cross-band in Menu #41 X-RPT).

Update 24Jan03:
With FT847-SuperControl it is possible to do a full crossband repeat including possible repeater shifts. Please have a look to available CAT software for the FT-847 transceiver to get more information.


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Auto Memory (Menu #36) Action in Satellite mode

When you are in satellite mode (SAT button on) and you use the MEM/VFO CH knob to change satellite memory channels, the action that results from that depends on the setting of the Auto Memory Menu setting (Menu #36). The Operating Manual does not do a good job explaining what this menu setting does. It's really much simpler than the manual suggests.

AUTO-MEM set to ON:

Each time you use the MEM/VFO CH to tune to a satellite memory channel, the two frequencies displayed will be the last frequency pair that you had set for that satellite memory channel to when you last used it. If you were out on the edge of the bands for that satellite, then that's where you will be when you switch to that channel the next time.

AUTO-MEM set to OFF:

Each time you use the MEM/VFO CH to tune to a satellite memory channel, the frequency combination displayed will be the frequencies that you set the channel to when you initially memorized the channel.

You can use this feature to your advantage either way. If you would prefer that the frequencies for a specific satellite channel always return to, say, the center frequencies for that satellite, then set Auto Memory to OFF. This is a convenient way to always return to a known place, and is suggested for people not intimately familiar with the frequencies for the various satellite bands.

On the other hand, if you want to return to the same frequency pair you were on the last time you used the satellite, then set Auto Memory to ON.

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FC-20 Auto Tuner.

The FC-20 auto tuner is available as an accessory for the FT-847 and the FT-100, and for a period of time the company gave buyers of the FT-847 a coupon for a free FC-20 (or the ATAS-100 antenna system). The FC-20 was designed specifically for the FT-847 and FT-100 and is intimately mated to them. The FC-20 is capable of matching a SWR up to 3 to 1 (but see a workaround on this). It features 100 memories that memorize your favorite frequencies so that when you return to them, the unit can "instantly" tune to a frequency without having to evaluate the SWR as it tunes.

People have identified two limitations to the FC-20, the matching range and the inability to use both CAT control and the tuner simultaneously. If you don't need a wide matching range and don't use the CAT control with the radio, then the FC-20 is reported to operate very smoothly and is well integrated with the radio.

Update 09Feb01: Joe KC5DFP reported on the bulletin board that he was hearing relays clicking when trying to transmitting SSB greater than 50 watts with the FC-20. He later tracked it down to a bad jumper cable between the rig and the FC-20. Problems with RF and other odd behavior have been tracked down a number of times to defective jumper cables or their PL-259s.

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Matching range.

Since the FC-20 is specified to match to a maximum SWR of 3 to 1, it will shut down when asked to match a load that presents a SWR of greater than 3 to 1. This is part of the design, and Chip Margelli on the Yaesu newsletter page (5/18/99-this discussion is apparently no longer available) discusses the design considerations for this tuner, that it is not intended as a wide ranging tuner, but more of a "fine-tuning" tuner.

Some people have written posts complaining about the limited range of the tuner, while others have said it works just fine for them. In any case, see the work around for a way to extend the tuning range.

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FC-20 Workaround for Matching Range Limits

Recent postings have identified a way to extend the tuning range of the FC-20 beyond 3:1. Apparently, if you press the Tune button and the FC-20 senses a SWR greater than 3:1, it simply shuts down and will not tune. On the other hand, if the FC-20 senses a higher than expected SWR when you are transmitting, it will attempt to tune it, provided you don't press the Tuner button.

Paul K8IDX said that he first tuned on a band that the tuner would match. Then he switched to the desired band and applied a carrier with some power. The tuner will attempt to tune. Mike K9JRI said he put a dummy load on Antenna port B, switched to that port to tune, then switched back to port A and applied some power. Don't press the Tune button, or you will have to start all over, since the FC-20 will then shut down and not tune.

Update 21Feb00: It seems, from these workarounds, that a rule of thumb would be to tune the FC-20 on some band (or dummy load) where it will tune properly, and then never bother to press the Tune button again. Just switch to the band of choice and key the rig; the tuner should attempt to tune it! Just like any other autotuner. I don't know whether you have to go through all this the next time you turn on the rig or tuner.

Update 14Oct00: Rob MW5EPA reports that he tried an experiment to see how this workaround did. He reports:
"When pressing the tune button on a higher than 3:1 SWR, depending on how high, the tuner may only put in about 30Watts to try and tune because the output is limited. In this case, tuning to a band with lower SWR and then jumping to that band without re-tune offers some success. On my experiment, the SWR was 5:1.On a normal tune power was limited to 20W.
When I dropped down [to another band where the SWR was lower] , fooling the tuner, I managed to nearly get the full 100W out. This however took about 3 seconds of carrier for the tuner to sort out ( Power would increase from 30-100W in 3 secs). Each time I keyed, the same three seconds were needed before the 100W. The higher the SWR, the longer it took & I think 5:1 was about the limit at which the tuner could give full power.After this limit, I noticed a drop in power and by now my FC20 was getting rather warm so I ended the tests. "This experiment was only attempted on one band. It may well be worth trying with about the same mis-match on every band to see if it's tolerance will change depending on frequency to tune. I also noticed that this was similar on 6M but I didn't take any time or power measurements. I am a little nervous about prolonged experiments for fear of damaging the tuner or set. "

Update 18May03:
It seems that there is a simple way to get a 7:1 matching range instead of a 3:1 range. David KI7WZ came up with that solution.
The first thing you need to do is get into the service menu of the 847. You do this by holding down the three buttons on the mic and turning on the
radio. The first menu will be Fm-51 do not change that one. Rotate the sub-tune knob until you see the menu that says SWR 3.0 to the left this you
will see two small numbers or numbers letter combination. Rotate the MEM/VFO CH knob until you see 9A then push the menu button and you are done. FC 20
Fix will tune a S.W.R up to 7:1 instead of 3:1 It works perfect. David KI7WZ


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Using the CAT interface and the FC-20 tuner at the very same time

There is a very simple solution to use both, the FC-20 tuner and the FT847-SuperControl CAT control software together at the very same time without any problems !!! It's untested with other CAT control programs, but they should work too. Please connect your FC-20 to the FT-847 transceiver. Please also connect the computer to the FT-847 using the nullmodem serial cable. Under normal circumstances if you try to start the communication with 57600 baud, you don't have success to get the communication between the computer and the trcvr working. Now please do the following trick: go to the internal transceiver menu and switch the CAT interface speed to 9600 baud, leave the menu then. Again please go to the menu and change the speed back to 57600 baud and from now on you are able to use both, FT847-SuperControl and your FC-20 tuner at the same time !!! It seems that this is a very simple solution. It was successfully tested with a european and brasilian version of the FT-847 transceiver. Vy 73 de Peter, DH1NGP

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Inability to use CAT and the FC-20 at same time.

This limitation is the result of a design decision for the radio. The FC-20 uses the same port as the CAT control, so you must choose between one or the other at any one time. This seems like a blunder since people are increasingly using their radios and computers together. One fix for the problem was described on the Bulletin Board, but there is no general fix available and Yaesu has said they did not intend to correct this limitation.

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Workaround for CAT & FC-20 Incompatibility

If you do not touch the tuner button after you turn your FT-847 on, apparently you can then use the CAT control and leave the FC-20 plugged in. If you use the tuner at all then the CAT control will not work until you again shut off the FT-847, wait a little, and then turn it back on. Note that at least one person claimed that this did not work for him.

Rick K1RDM reports that he installed a simple A-B switch in the control line between the FT-847 and the FC-20. Using this, he can switch his FC-20 in and out of the circuit and thereby use CAT control once he's tuned up. He reports that he turns the rig off, switches the FC-20 out of the circuit with the box, and then turns the FT-847 back on. The switch is replacing the (wearing-plugs-out) operation of unplugging the FC-20 from the rig in order to use the CAT control. Rick also reports that he has done hot-switching with no ill effects (on his rig at least) but makes no representations that doing the same won't harm your radio.

The box comes with a pigtail and jacks so you're ready to plug the box in once you get it! No mods!

Manufacturer: Advanced, AESP
Part NO: 13218
Supplier: Computer Town
Salem NH
Phone: 800-666-0004
Price: $19.97

Rick did need to trim about 1/8" off the vinyl shroud, on the Yaesu supplied cable, to allow it to fit the MiniDin 8 receptacle on the switch. In addition, the switch is supplied with a pigtail that does mate with the radio.

Others with workarounds on this are encouraged to post them on the bulletin board.

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Stock Microphone

The stock microphone, the MH-31B8, does not have DTMF buttons on it. It does have buttons for UP, DOWN, and FAST on the front. Press UP or DOWN to move by the setting in Menu #2 MIN-FREQ. Holding down either button starts scanning up or down. Pressing FAST raises the step rate by a factor of 10.

There is a small switch on the back, marked "1" and "2." It does not seem to have much (any?) effect. Some say the "1" setting gives a more full-bodied audio and "2" is sharper. It's extremely subtle to my ears.

The hand microphone is necessary to access the alignment menu. Click here to view the FAQ on the alignment menu.

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Other Microphones for FT-847

People write to the Bulletin Board seeking information on alternative mikes for the FT-847. This posting summarizes the experiences of others. Generally, mikes optimized for SSB don't seem to work as well on FM, and vice versa. But read on.

Mike KE4LGL reports that a Kenwood MC-60 works well, including the Up and Down buttons.

Tom AA2VK reports that he uses a Heil Proset with HC-5 element and reports that "everyone says it sounds fine for FM and SSB." (I use this setup as well and have the same report.)

Jerry DK2FI reports that he uses a (desk?) mike with the Heil HC-4 element. This is good for SSB, but not for FM.. He tried a Shure Model 450 and reports that it works great on both FM and SSB.

Robert M0AOV reports that he uses a Watson WM-308 and that it works "brill" in both FM and SSB and that the Up and Down controls work properly, too.

Bob N5NJ reports that he uses a Heil HM-10 with both HC-4 and HC-5 elements. He reports that the HC-4 works fine on SSB and the HC-5 on other modes and to ragchew on SSB.

Those using the Heil Proset will need to obtain a footswitch (or some other way) of keying the PTT on the rig, since the Proset has no PTT. Heil sells a footswitch, but you can use anything that will close a circuit. (I used an old surplus footswitch that I had used to turn on an photo enlarger light). It plugs into the external PTT on the rear of the rig.

Update 11/22/99: Jerry DK2FI swapped mikes again and reports, "I received my HEIL 'Goldline' microphone 2 weeks ago. It contains a 'Full-Range' element and a HC-4 for DX-ing. I used a Shure 450 before and thought it's the best mike for this radio but friends, with that new "Heil Goldline" I received fantastic audio reports (SSB AND FM). They all say 'broadcasting quality' and every 2nd QSO somebody is asking me what kind of mike I'm using. Just want to share this experience with you." I have heard similar reports from two other hams.

Update 12/11/99: Ted N3ZRX reports that the Yaesu MD-100 microphone works on the FT-847 right out of the box. He goes on to suggest the following setup for using this mike to get the best sounding audio: Turn on the extended menu by changing Menu 42 EXTEND to ON. Then, adjust Menu #92 USB-CAR and Menu #93 LSB-CAR to "-10" for both. This extends the bottom end audio range on SSB. Then, on the mike leave the Filter on at all times. For SSB set the High Emphasis ON and the Low Cut OFF. For FM, set these two the opposite: High Emphasis OFF and Low Cut ON. Ted reports that these settings have been tried and proven by KF2JG and AA3RE and himself.

Update 09/28/00: Harry KC3MX reports that he's been using a vintage D-104 mike with "fine" results. He also found that the stock mike didn't sound good with his voice. Harry said that different people sound different on the various mikes, and you just gotta try 'em until you get one that sounds good for you. It's all a matter of taste.


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Roger Beep circuit designed for the FT 847 (installed into microphone) by OK1VPZ - Updated 23May2003

Please see the picture of the circuit >>here<<

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Chattering or Clicking Relays, Display Dims on TX - Updated 21Mar01

 

Some hams have posted to the Bulletin Board, reporting on chattering relays, dimming or loss of displays, when transmitting. The problem is most noted when using high power. Apparently, either low battery voltage or RF getting into the rig from a poor cable or jumper cable will produce these symptoms. Examples of experiences are noted below. I have seen many postings on the Bulletin Board that were resolved by replacing a jumper cable or connectors on them.

George KA3WXV reported on 12Jun00 that a low voltage situation will produce the following symptoms in the FT-847: the display dims and the relays chatter. If you are having these two problems, you might want to check the voltage and current that's actually available to your rig from your power source. Another possible problem comes when using a switching supply. In certain proximity to the rig, certain switching power supplies can interact with the rig. If you are having "FMing" reports on your TX audio or strange actions with your rig, try moving the power supply away from the rig to see if that clears up the problem.

Joe KC5DFP reported in early 2001 that he was having problems with chattering relays and a dim display when transmitting with greater than 50 watts. He traced this problem down to a poor jumper cable between his FT-847 and the FC-20 tuner.

Kelley W0RK reported that his display would dim or go out completely and then come back on when transmitting on high power, but all was OK on low power. He surmises that RF was getting back into his rig via a PL-259 that was not seated well on the back of the FT-847. Once he got it seated properly, things were back to normal.

Update 21Mar01: If you're having chattering of relays when ending a PSK transmission, the problem is more likely with your interface. In this case, click here to for a hint on what to change.

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Chattering Relay fix - Updated 11June03

Adobe PDF document of this modification (211 KB)

As I got my FT-847 (serial 8F043xxx) I recognized the chattering relays after a short time of usage. I'm not using a switching power supply
cause of some interferences or noise levels of this. I'm using a MANSON EP-925 regulated power supply with 3-15 Volts / 25-30 amp.

So the "chattering relay fault" is definitely not cause of the usage of switching power supplies or cause of RF feedback like published in this
forum before. I had the same bad effects on the dummy load too. Hmm, so the fault must be on another side....

I disconnected the vhf/uhf pa module. The effect gets better but still was there. I disconnected the hf pa module. And the effect has gone !!!
So the fault must be in the hf pa module ! Now I did some tests of connecting/disconnecting the pluspole of the hf
pa module cable while the FT-847 was running. And I saw a small flash everytime I connected the cable to the pa module !!

So overvoltage on switching on the FT-847 was the fault ! And a lot of DC power supplies have a build-in overvoltage protection too. So when
the FT-847 has the short overvoltage, the DC power supply reduces its voltage output too, the FT-847 internal overvoltage relay RL1001 goes
off cause of the reduced DC input, and then the DC of the power supply can go up again, a overvoltage peak in the FT-847 is the result, RL1001
goes off again,....

...and we just have the loop ! RL1001 on the AF-CNTL-Unit is chattering.

Here's the fix:

1. None, really none of the bandpass switching relays on the PA-UNIT have a antiparallel overvoltage protection diode (suppression
diode !??) ! So I soldered 1N4148 diodes parallel to each relay coil of the PA-UNIT. So that means parallel to RL5001 - RL5015. Only the HF output relay
RL5016 has a overvoltage diode (D5005). The cathode is on the pluspole of the relay coil, the anode is on the
ground side. So these diodes don't have any action on normal use, but when the relays go off their coil is producing a overvoltage peak. These suppression
diodes eliminate these peaks. The chattering got a little better, and had sometimes gone, but this wasn't the real fault.

2. Now I gave the FT-847 internal overvoltage protection circuit (consisting of Q1118/Q1122/RL1001) a longer reaction delay. It's a real
simple mod and works fine without any problems till yet ! You can solder very easily cause the neccessary parts have enough room for this mod and
you don't need to remove the AF-CNTL-UNIT.

AF-CNTL-UNIT:
- 1N4148 suppression diode parallel to coil of RL1001
I soldered it from D1039 to D1041 like in the picture.

(>> Please click here for a detailed picture #1<<)

- Adding a 470µF (0.47mF) electrolyt capacitor across this supression
diode. This cap is parallel to the relay RL1001 and gives it
the needed fallback-delay. The pluspole of the cap is looking toward
D1039, the minuspole toward D1041.

(>> Please click here for a detailed picture #2<<)

Since this mod I really can enjoy my FT-847.

73, Jochen DG2IAQ
Echolink DG2IAQ-L, node #69306

Update 24Jan01:
new complete modification sheet by Jochen Heilemann, DG2IAQ


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ALC Control of RF Power Output

Some of you might want to use the FT-847 with an amplifier or transverter. Many amplifiers provide ALC feedback to prevent the transmitter from overdriving the amp. Transverters don't often have such protection, but you can provide ALC control to your rig to keep the RF power out within the limits of the transverter.

Rick VE3CVG recently reported the results of tests he did by adjusting the negative ALC voltage and measuring the resulting power out. Rick's report is reproduced below. Keep in mind that, if you lose your negative ALC voltage, then your FT-847 power output will rise to whatever level you have set with your RF Power knob.

"I performed some simple tests on the ALC circuit of the FT-847 with a view towards limiting the power output so that the radio may be connected to a Down East Microwave transverter. I was really pleased with my findings.
Bias(V) RF out max. Notes
-1.190 10w RF Out control reduces output pwr when set between min and 9 oclock
-1.155 5w RF Out control reduces output pwr when set between min and 9 oclock
-1.213 2w RF Out control has barely perceptible effect on output pwr below 9 oclock
-1.250 1w RF Out has no visible effect
-1.286 .50w RF Out has no visible effect
-1.313 .25w RF Out has no visible effect
-1.410 few mw RF Out has no visible effect
-1.510 not visible RF Out has no visible effect

"Readings were taken with the FT-847 set for 21.100 MHz with mode set for FM. Bias measured at RCA-type ALC jack on rear of FT-847 using a digital multimeter set on 2000mv. RF level approximated from MFJ949E tuner/swr bridge set for 30w (full scale).

"Power supply made from 9v wall wart into an 8v 3-lead type regulator. 2k, 10-turn, variable resistor across output. +V lead to gnd of FT847, tap on variable resistor to ALC connector. When the radio is keyed via the PTT button on mic, the bias voltage drops 3 mv. All bias voltage readings above were measured while radio PTT was keyed.

"PLEASE NOTE - this is for info only, your radio may give different results. Please let us know what you find. I still want to measure the actual current drawn by the ALC circuit, but I know that its small. I will repeat the tests at 144.200 MHz.

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Clarifier (RIT) & Sub-tune Properties

Kresten OZ1ALF wrote to ask if he could adjust something so his RIT knob changed the frequency quicker. He was referring to being in the middle of a contest, trying to zero in a station on RX. The RIT turns at 1/10th the rate of the main VFO. You can adjust the main VFO tuning rate by changing Menu #2 MIN-FREQ so that it covers 100 Hz, 1 kHz, or 10 kHz per revolution. In each case, the RIT knob turns at 1/10 the rate.

The FAST button, which speeds up the main VFO by a factor of 10, has no effect on the RIT rate.

A workaround, suggested by Mike K8LH, was to run split operations. If you set your TX on the sub-vfo, then you can use your main VFO for RX. However, this then makes it tedious to tune around the band looking for signals with the main VFO, and then having to "chase" them with your sub-tune for transmitting. You could simply do A>B when you found a station to load the sub-VFO.

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