Antenna Connections on FT-847

The FT-847 has four separate antenna jacks on the rear panel, one each for HF (all HF bands), 6m, 2m, and 70cm. Three of the jacks take PL-259 plugs, and the UHF jack takes an N plug. There is a menu choice in the radio to have 6m signals go to either the 6m jack or to the HF jack. This is the only combining possible inside the radio. The radio routes the appropriate signal to/from the appropriate jack, depending on which band you're tuned to on the radio.

If you're planning on using multi-band antennas, as in 2m/70cm or HF through 70cm with the ATAS-100, you will need a duplexer or triplexer to manage signal combining. Some hams have reported good results with some du/triplexers, and others were disappointed. In order to use the ATAS-100 antenna system with the rig, ensure that any du/triplexer will pass DC through the center coax lead, since that's how the ATAS-100 is controlled. You can use the ATAS-100 for all bands 40m through 70cm. To do that, you'll need a triplexer (HF/6m, 2m, 70cm). Three reports below discuss using the Comet CFX-514 and CFX-514J on all bands.

Mike KF6SWI reported that he used a MX-2000 duplexer for a while with his rig.

John KD7HDM reports that the Comet CFX-514 with coax leads works well, and that you need a N adaptor for UHF.

Alan G8XLH reports on the CFX-514 as well, and says, "I use the Comet CFX514 (Without the J) and the flying [coax] leads, connect directly to the radio without any adaptors. The Freq split between ports is good for me because in the UK we have 4 Metres (70Mhz) which appears on the 6M 50Mhz port, where some couplers cut off just above 50Mhz.

John, KB9MIE, reports the following, and I'll quote him for accuracy: "I am using the Comet CFX-514J. 1.3-90 MHz, 130-200 MHz, and 380-500 MHz. The spacing of the two lower frequency ports match the spacing of the 2M and HF ports on the FT-847. I am using UHF male to male joiners and F->M elbows to directly attach the triplexer without cables and have it lay parallel to the back of the radio. The 432 MHz port is connected via a short length of cable to the FT-847 432 MHz port. Power handling capacity of the triplexer is 800W PEP on lower frequencies and 500W PEP on 432. Losses are less than 0.15, less than 0.2, and less than 0.25 dB."

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Power Switch Problems Updated 15Jul01

A few people have reported on the bulletin board that their power switches failed. Typically, they won't stay locked on, which is a mechanical problem. Gary N5IXI reported that his switch had burned the contacts. Short of getting a new switch, hams have reported the following temporary or permanent fixes.

One fella jammed a toothpick along side the switch to hold it on. Another took the switch out and flipped over the sliding part, since half the switch is not used at all. Another suggested that you could swap the switch with the MOX switch, since they're identical and the MOX is not used that often. Another ham said that he never turned the rig on with the power switch; he used the switch on the power supply instead. Others expressed concern over this, worried about transients from the power supply harming the rig.

You can click here to read about how to disassemble your rig in order to replace the power switch yourself.

Update 08Jun00: Peter OZ1PIF today reported the following: "In the back of the front assembly, just behind the on/off switch, there is a little piece of aluminium glued to the frame. During transport to Greenland (For the OX2K dxpedition) it fell off and shorted the on/off switch, resulting in a fried circuit trace. Remove it first chance!" I don't recall seeing that on my rig, but I have a lot of "moments" so don't rely on me.

Update 15Jul01: Eddie G0EHV reports that Yaesu is now supplying a fix for the power switch. It's apparently just a 10 ohm resistor to reduce the current through the switch. Eddie reported that he did not install the resistor because it looked like more trouble than it was worth. You might want to consider adding a 10 ohm resistor in the circuit to the power switch. The bulletin insert that comes with the switch also describes strapping the left and right sides of the power switch together to divide the switching current between two contacts. Keep in mind that mechanical failure is not addressed by this fix.

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Power Switch Modification Updated 23May2003

I've read about and have always worried about the power switch! Though my power switch has showed no problem as of yet (maybe because of the lack of use) I ran across a idea that I couldn't resist and it has turned out terrific. My power switch now only conducts 30ma of amperage-Interested!!-I was!!!

While at Radio Shack I noticed a small 12VDC relay @ 10 AMPS Contacts that looked small enough to mount behind the front panel!! Still interested? I was!

So for $3.99 I took a chance that my memory was still active. The following photos shows how perfect this relay fits. It's as though it was made in heaven! The wiring is pretty much straight forward so you shouldn't have any problem with it, especially with the photos. Basically, the original green and white wires to the circuit board plug(on the front panel) were cut and re-routed to the relay switched contacts. Then I tapped 12VDC at the rear power connector BEFORE the relay switched + 12vdc(activated by the front panel power switch) and spliced that to one the front panel plug leads that was cut(Orange wire).Then the other lead of this front panel plug was connected to one of the NEW relays coil contacts(Red wire/White tracer).The other lead to the NEW relay's coil was connected to ground(Black wire). As shown in the photos, the relay was mounted with double sided tape next to to cooling(unbelievable perfect fit!) fan and high enough to clear the phone plug circuit board when the front panel is tilted back into place. Now the power switch only conducts the voltage and current to activated the NEW relays coil! Oh, life is GOOD!

Pictures of the modification: 01 02 03 04 05 06 07

Use this information any way you please so other users can quit dreading the Power Switch gremlin from visiting their shack's.

The Radio Shack Number for the relay is RS-275-0248A (reported by Art Lund-NQ3A)

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Power Switch 10 minute repair method Updated 23May2003

I had problems with power-on button. Temporary solution is very simple, so you may repair your radio and easily look for more time to replace original switch.

After you take out both upper, and bottom covers, you may unscrew upper display panel holding screws, and slightly loosen lower ones. Your display will fold toward you, so PCB will get accessible. At the left side toward you, there is power switch to be patched with two small pieces of wire. (another pair of contacts is not used by Yaesu, so we may use it here. Please see final picture of the modification >>here<<. (reported by Emil SP5LBS)

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Using Built-in Keyer for CW Practice

This is a recurring question, whether one can use the internal keyer for practicing CW. For those who already have some CW privileges, I recommend that you practice with another ham on the air; there's nothing like it for increasing your proficiency quickly. But, a ham with a no-code license who wants to get a code license might think it would be handy to use the rig's keyer for code practice.

There is no way to use to the built-in keyer without transmitting. If you try to, say, tune the rig to an out of band frequency so the TX won't work, well, neither will the keyer work. You could turn your power all the way down and connect your rig to a dummy load, but even this will probably put some small amount of RF out into the air. Best bet is to get or build an inexpensive oscillator that you can use with your key or paddles.

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Grounding Problems and Other Noises Updated 15Jul01

Guy W4NUS reported in November 99 that his rig would suffer from a loud burst of noise on 432 when he switched to that band and had his preamp turned on. It also did it when he keyed the transmitter on that band. The noise would last about 15 seconds. He tracked the problem down to the RF board. The "green coating" (I assume solder mask material) covered some of the circuit board where the mounting posts attached. He cleaned those areas down to the copper and reinstalled the board with star washers on the posts. This cured the problem completely. He reported that the rig was very quiet and stable.

A number of others have reported that they have many birdies on 15m and 10m. This has been tracked down to soldering flux left on the DSP board where it mounts to the mounting posts. It appears that a good place to look for solutions to ground type problems and birdies (in addition to the other equipment in a typical home) is in the grounding of the boards.

Update 20Jul00: A while back Ger PE1CZG reported on some odd noises that he could hear when he turned the VFO, but not when it was not turning. This month Walt K4WDE reported what he called a "frying" noise at 7.290 and also at 2.025; he reported that the scratchy noise only occurred when the VFO was changing but not when stopped. I duplicated the noise at 7.290 but not at 2.025. It was very weak on my unit and would not even open my squelch on USB.

Ger wrote in yesterday to say he cured his noises by improving the grounding of the circuit boards in the rig. He did this by removing the screws attaching the boards to the chassis and scraped the mounting locations cleaner with a knife. He reported that the problem was cured this way. Dave WB5HJV just reported that he applied Ger's fix and the noise went from S5 on his unit down to nothing when an antenna was connected. Finally, Harry KC3MX reported on a similar noise and fix on a Kenwood TS-680S.

These reports certainly support the theory that improved grounding will eliminate a variety of small buzzes, birdies, and bursts. See also Birdies, below.

Update 08Aug00: Henk PA0CIS reported that he had a similar noise transient when switching to 432 MHz and each time the rig transitioned from TX to RX. He tried the fixes mentioned in the FAQs, grounding the boards, but they did not completely cure the problem. His modification to the rig is reproduced below for others:

"During switchover to 432 and during the transition from tx- to rx-state a strong noiseburst occured. In the FAQ's some cures are given, e.g. better grounding of the PC boards. I tried all of the suggested cures, but it did not help 100%. (I even took out the VHF/UHF PA board and improved the grounding).

Analyses with a spectrum analyser showed an oscillation of the 432 pre-amp during the switching transient.

The cure is as follows :

Remove the rf board completely.
On the solder side cut the connection between the gate of Q3004 and the combination of R3015, L3010, C3018 and D3096.
Cut as close to Q3004 as possible (between R3015 and Q3004).
Take a small ferrite bead (4mm) and run 2,5 turns of 0,4 mm insulated transformerwire through its centerhole.
Make sure the wires are within a 180 degree arc, allowing you to mount the bead close to the PC board.
Solder one wire directly to the gate of Q3004. Solder the other wire to C3018. Keep the wires as short as possible (and do not try to reconnect to R3015)
Press the bead almost against the PC board and ad a little drop of 10 sec. glue between the bead and the board.
Replace the board and reconnect all connectors.
Around 432 Mc I could not measure any degradation of sensitivity. (I did not check the rest of the frequency range)
It's quite a pleasure to QSO on 432 without the constant noisebursts in your ears..."

Svein LA6PV reported that he did this mod and it cured a similar problem for him.

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Some early FT-847s had problems with numerous birdies, especially on 15m and 10m. The company stated that this was likely due to "excess flux" on the DSP board and that removing the flux would correct the problem. Only some owners reported this problem. A recent posting suggested that the flux was preventing a good ground for this board, so that may be the problem with the excess flux the cause.

Another likely explanation for birdies is actually the equipment in a modern home: PCs, printers, VCRs, satellite control boxes, baby monitors, "wireless" phone jacks, and other electronic gear. There is a proliferation of noise generating devices in the home. Many will generate noise even when turned off. The FT-847 is very sensitive and, if you have good antennas on it, will pick up a wide variety of spurious signals.

In order to test your radio, you will have to make sure that you have actually eliminated any signals coming from your home or from your neighbors' homes. Remove all antennas and replace them with dummy loads. Then, you can tune around the various bands and see what birdies you can hear. Any birdies that you hear could be internally generated in the radio.

Many people with birdie problems have found that they were, in fact, coming from other equipment in the home.

Update 11/29/99: Dave MW5ADJ reports as follows: "I found that there were quite a few birdies in the range from about 20 Mhz to 30 Mhz. I had read about the problem with the dsp board having too much flux left on it, so I removed mine from the radio and found that this was the case; i.e. the board was not earthed to the casting due to the flux provideing insulation at the 4 screw holes on the underside of the pcb. After cleaning this off I found it made a fair improvement! I must stress though that this might not be the case for all. Hope this is of some help." Dave's radio is in the 8H series, meaning it was new in mid-1999.

Update 12/11/99: See also the FAQ on Grounding Problems for another situation where Guy W4NUS solved a feedback problem by cleaning up the mounting area for the mounting posts.

Update 15Jul01: The "frying noise" that people have reported on certain frequencies when turning the VFO dial are apparently digital noise emanating from the front panel. On certain frequencies, I have been able to hear all of the rotary knobs making a rapid clicking noise as they are turned. Since all the rotary controls provide digital input to the CPU, they produce these frying noises when RF products fall into the frequency range that's tuned. If you have an INRAD crystal filter installed in your rig, apparently the positioning of the RF cables from the filter to the plug-in board can pick up front panel noise. If you have this problem (and it bothers you), try repositioning the cables from the filter. Stuart G1IDE reported that he found that his ground pin was an open circuit. Replacing these pins solved his noise problem. Ken AH6LE reported that he eliminated the frying noise by relocating his RF cables.

Update 24Jan04: I had the same trouble with mine. I did the following mod to fix the problem:
The reason was grounding problems in the DSP Unit. To fix that you have to open the DSP box behind the frontpanel, unsrew the PCB and and remove it.Now you have to clean the PCB grounding points with a glas-fiberbrush, or something similar. The PCB grounding points are covered with plain varnish, that's the reason for the bad grounding. Now you can reassemble the unit, and hopefully enjoy your FT-847. This mod worked fine in my FT-847, and all birdies were gone. As always: Do this mod on your own risk! 73's de DB8BS

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5 pin mini-DIN plug for amplifier control

The FT-847 requires a 5-pin mini-DIN plug for controlling amplifiers with the FT-847. These are not available at your local RS store. Hosfelt in Ohio sells them for $1.12 each. Correct US phone numbers 888-264-6464 or 800-524-6464. Fax 800-524-5414.

One poster said that he simply took a 6-pin mini-DIN plug for a PC mouse or keyboard, clipped the 6th pin off and it worked just fine. If you look at the schematic, you will see that the pin layout for 5-pin and 6-pin are identical (except for the 6th pin, of course). You can also get a 6-pin mini-DIN plug from your favorite RS and do the same surgery.

Mike K8LH said in early July 1999 that, if you call or email Yaesu Tech Support, they will send you the 5-pin mini-DIN for free and the 6-pin one. Mike said that Yaesu said the plugs were supposed to have been included with the package. Nice of Yaesu to do this! The part numbers are P0090976 and P0090819.

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DC Power Cord

The 6-pin DC power cord for the FT-847 is common with some other rigs (Icom, Kenwood), so you might be able to substitute one of those brands of cords if you need another one. Because of the high currents, so you must make sure that any replacement power cord uses the same pins for the same voltages and that the cabling is large enough to carry the current. See also the warning about hooking up cables backwards!

People have reported finding some of these plugs with wire at hamfests.

Update 18Apr00: Jack N7ONC reports, "I have found the Waldom/molex power connector part number 19-09-1069-P is an exact fit for the 847 and other HF rigs. It is available from digikey or mouser for less than a $1.00 plus a little shipping. Just remeber to get the crimp terminals with it."

Update 25Mar01: W4RYW reported that he ordered part number 538-19-1069 from Mouser and it wouldn't fit; it was a little large. Anybody know of a better source?

Update 26Sep02: Delbert reported that they are NOT Molex brand. They are slightly smaller molex copy from Japan. The Molex number that used to be in the faq section (may still) is wrong. The Molex part looks correct but it is a little larger and WON'T work. I found out the hard way! I purchased the correct connector pins and hood for about $6.00 US, a little high on price but it was correct. I can't remember the vendor but they had a banner ad on eham.net ??CableXperts??

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VOX on the FT-847 - NOT

There is no VOX control on the FT-847.

If you want VOX, you will have to adapt an external VOX setup to your Yaesu 8-pin mike plug. There are kits you can build, microphones with VOX built in, and a recent ad for an Icom External VOX modified for the FT-847 shows that other commercial VOX units can be modified for the FT-847.

Update 01Jan01: Inrad, the makers of filters for many ham radios, is about to offer a VOX box designed specifically for the FT-847. They report that the units will be available shortly. Check it out at http://www.qth.com/INRAD/ for more info.

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ARS on 10m & 6m

The FT-847 has Automatic Repeater Shift (ARS), unless you do the mod to open the transmit. However, the ARS is only active on 2m and 440. You can select offsets when in FM mode on 10m and 6m, but it is a manual selection and not automatic.

When selecting an offset on 10m and 6m, you must first be in the FM mode. If, once you have selected an offset, you switch to SSB or CW, the offset will not turn off (nor can you turn off the offset until you go back to FM first) and you will transmit according to the offsets set in Menu #16 28M-RPT and Menu #17 50M-RPT. On 2m and 440, the offset will automatically be canceled when you switch modes to SSB or CW. See p. 52 in the Operating Manual for a discussion of this feature.

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Tuning knob wobble

The main VFO tuning knob on some (most?) FT-847s has a slight wobble in it. One poster said his wobble was so bad the knob hit the ring behind it; he returned the rig for another, but most have simply noted it and moved on. A couple of people said all Yaesus were like that!

I took the rubber ring off (with great effort) and found no set screws underneath it. I examined the exploded parts diagram and could find nothing suggesting a set screw. Well, it turns out you don't need to remove the rubber ring at all. Dave WB5HJV reports that you can access a small set screw through the narrow slot in the bottom of the shuttle ring; this will enable you to remove the knob. He suggested using a flashlight to see the screw. He also reported, however, that the knob consists of a brass insert that is set into a plastic piece. The plastic piece, apparently, is the thing that is out of round. There still appears to be nothing to do about a wobbly knob short of exchanging it.

At least now we know how to get the knob off. Thanks Dave.

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Hooking up power backwards - DON'T!

Be very careful you do not hook up the 12V power to your rig backwards! Although there is a protection diode for much of the circuitry, if you hook up the radio backwards, you will probably blow a 5V regulator and a capacitor that are used to maintain the rig's memory. These are outside the blocking diode and are therefore not protected. You can see this on the schematic, on the upper right of the AF-CNTL circuit board.

There is a Caution message in the Operating Manual (on p. 7) about this.

Update: One preventive measure you can take is to install a large diode in series with the main power cable to the radio. It must be able to handle the normal current of the rig (~22 amps). If you hook up the rig backwards, this should prevent a reverse flow of current. You will have about a 0.6 volt drop across the diode, so you might want to tweak up your power supply, if possible. You're on your own here!

Update 06Aug00: Randy KB9POI reported that he did the Big Boo-boo and hooked his rig up backwards. He sent it to Radio City for repairs which cost him about $167. He said the invoice showed that they took out the DSP board, disassembled the front panel completely, replaced a 5v regulator, and 8v regulator, and also replaced the power switch. Apparently at the same time, they did an alignment on the radio because it works better than it did before.

Update 28Sep00: A ham who requests to remain unnamed reported that he did The Dumb Thing, too, and he blew up a 1000 mF capacitor next to the back-up battery. He replaced the capacitor and said the rig has worked fine since then, with no loss of memory channels.

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SWR Indicator

The FT-847 does not have a SWR meter built in. What it does have is a "high SWR" indicator (in the upper right corner of the display) that comes on when the SWR is greater than 3:1. It also needs to see a fair amount of power before the indicator will come on. This indicator works whether using the FC-20 or not.

Update 11/19/99: I heard from Alan (KD7FLV) that his high SWR light never came on, even when it should have. He shared that Yaesu told him that the high SWR indicator only functioned when the FC-20 or ATAS-100 was connected to the rig. I do not have either of these accessories, and I have abused my rig enough to know that the SWR on mine (8G05 series) works as a high SWR indicator just fine. Perhaps the firmware was changed since my radio to behave differently in this regard. Could explain why some say theirs never comes on. I do have to push some power in order for the light to work but it otherwise behaves as one would expect as a high SWR indicator.

Update 28Jan00: Alan had written a while ago to say that he had a coax problem and that his SWR light did come on when the SWR was high. So, Yaesu's wrong (!) on this count, and the SWR indicator does work whether you have a FC-20 or ATAS-100 connected or not. Maybe this settles things.

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CAT Cable Between Rig & PC

The FT-847 requires just three wires for CAT control. These are RXD, TXD, and Ground. On a DB-9 connector, these are wires 2, 3, and 5. On a DB-25, they are wires 2, 3, and 7(?). In looking at the schematic for the radio, the various control lines are hard-wired "on," and the radio is using only the three lines. Also, there is no handshaking, as far as I can tell.

The cable between the PC and the FT-847 is called a "null modem." All this means is that wires 2 and 3 are crossed between the plugs at each end of the cable (i.e., pin 2 on one end goes to pin 3 on the other end and vice-versa). You can buy a null modem cable, or you can buy a straight serial cable and a null modem adaptor that goes in line (and swaps wires 2 and 3-and probably some others).

You can also make your own cable. Use shielded cable with three or more conductors (you could use the shield for ground, but I prefer to have a separate ground conductor). You will need a female DB-9 plug for the rig end and either a female DB-9 or a DB-25 plug for your PC, depending on what type of serial port you have. Newer PCs seem to have standardized on female DB-9s for the plug ends.

You will need hoods for the plugs, too. These can all be purchased at your favorite RS store, if you like, except they don't appear to have three conductor shielded cable, only two conductor plus shield. That works, too.

Update 14Feb00: Rick WZ2T reports that, in fact, RS does have a four conductor with double shield cable that would be good for making this cable. It's part number 278-777, $8.99 for 30 ft. Rick did report that it took the store personnel half an hour to find it, and that it was in with the speakers.

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Split operation

The Operating Manual is messed up in its explanation of split operation. See p. 63 in the manual. If you push the SPLIT button, the radio will be set up to have the main VFO display the RECEIVE frequency (not the TX frequency as the manual says) and the sub-VFO display the transmit frequency. This is the opposite of the text, but the picture is correct.

You can swap the TX/RX function, however, by pressing the REV button when in the split mode, so the main VFO will then transmit on the displayed frequency and the sub-VFO will now receive on the displayed frequency. Note that if you use the REV button, the frequencies don't swap, just the RX/TX indicator.

To have this whole page of instructions make sense, add a step 3A "Press the REV button" after setting up the split as described in the first three steps in the manual. Then things should make sense in the rest of the instructions.

When operating in the split mode (and NOT reversed), remember that even if you change the main VFO frequency (or bands, for that matter), the radio will still transmit on the sub-VFO frequency and mode! It is a good habit to always turn off split mode before you change main VFO frequency or bands or you will embarrass yourself.

Click here to read about using a narrow CW filter in the split mode with PSK31.

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Number of memories

Yaesu has advertised the FT-847 as having 100 memories. My Operating Manual says the channels are numbered 1 - 99. This information is incorrect. The radio actually has more than 100 memory channels, but they are not all available in the manner you normally expect. There are 78 general purpose memory channels that you can program. In addition, there are 20 "Smart Search" memory channels (FM only) where you can let the rig automatically scan from a center point until it picks up 10 stations above and 10 stations below your center point. There are 10 full duplex satellite memory channels which include tags. There are four Home memory channels and one Quick Memory "Bank" channel. Finally, there are at least 24 band stacking registers that remember what frequency you were on for each band and for VFOs A and B.

None of these different types of channels are immediately interchangeable. You can, for example, pick one of the Smart Search channels and then write that information to one of the 78 general purpose channels, but you can't change the arrangement for how the radio uses the various memory channels.

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Early Model Problems

Generally, prior to the 8G05 production run, there was one main problem in the design of the radio: it only had unidirectional CAT control for frequency and mode (i.e., you could only use the PC to command the rig but not to report the rig frequency and mode back to the software on the PC). Beginning with production run 8G05, the radios have bidirectional CAT for frequency and mode (PC commanding the rig, and the rig reporting information to the PC). In the USA (at least), Yaesu offered to upgrade all radios older than 8G05xxxx under warranty, which involved replacing a computer chip in the radio and some other modifications. Many people with earlier rigs took Yaesu up on their offer.

When Yaesu had these radios for upgrade, they would usually also upgrade other irritations noted elsewhere in this FAQ.

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Online FT-847 User Manual

Bill N5ZTW reported a possibility to download an original FT-847 users manual in Adobe PDF format. You can download directly from the Yaesu Web Site:


Unfortunately we don't have any information about how long this FT-847 user manual will be available for download on the Yaesu site.
Please report back any dead links. Thank you.

Update 24Jan04:
The FT-847 operating manual no longer appears to be available as a PDF
from www.yaesu.com. However, it is available from G4YNV

Update 24Jan04: I was just looking at the revision log and tried to get the 847 online manual. It's no longer at the URL given. A search on the yaesu.com site for
operator manual, search in files came up with all the online manuals. It's a long url, so maybe just a recommendation to do a search once someone gets to the yaesu site would be more efficient.73 de rick wz2t

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