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eHam Forums => Amplifiers => Topic started by: KB1TJY on December 22, 2012, 03:41:35 PM



Title: ARB-704 / Tuner Port REALLY a safe alternative?
Post by: KB1TJY on December 22, 2012, 03:41:35 PM
I just purchased an ARB-704 for use with my Yaesu FT-450D. I also purchased a PNP Cable (PNP-8M) to connect the two. The FT-450D does not have any RCA jacks on the rear but does have a 8-Pin Tuner port and an 6-Pin DATA port.

The cable I was told to get is the PNP-8M. Normally this 8-pin cable would connect to the DATA port. However, the DATA port is only 6-Pin. What Ameritron did to work around this was as follows:

"ARB-704 Interface cable for Yaesu FT-817/840/857/890/897/450*/950* (If this is for use with the FT-450 or FT-950, it connects to the radio's "Tuner" port rather than the 10-pin "Linear" port. Yaesu charges a premium for the use of their 10-pin connector, so Ameritron chose to make a cable that works off of the tuner port! This lets you, the end user, accomplish the same results with a cable that's a third of the cost.)".

Ameritron has some good product but I've been to hell and back with them on some products and I want to make sure that connecting that to the Tuner Port isn't going to fry the radio. (Why they are referencing the 'Linear' port I do not understand, as (1) a cable is currently running from it to the Amp's Relay AND (2) it's 10 Pin and not 8-Pin).

The Amp is an Ameritron AL-80B.

Does anyone know if this will in fact work when connected to the Tuner Port? And does it interfere with the functionality of the Radio's built-in Tuner?

Finally, I've read other posts here where the ARB-704 just isn't needed. Any input on that greatly appreciated.

I don't want to lose the built-in Tuner. Having said that, how do I connect this?

Thanks,

Lyman
KB1TJY


Title: RE: ARB-704 / Tuner Port REALLY a safe alternative?
Post by: N4NYY on December 22, 2012, 04:34:35 PM
Lyman, I was working at HRO and we had a similar situation today with an FT-450 and an AL-811. I think the 704 is used as a buffer between higher keying voltage amps like the SB-200 or such, so it does not blow out the keyer. Someone correct me if I am wrong. We were still trying to figure out the cable mess to see if there was a typo or mistake on Ameritron's website. But that was rather frustrating today.


Title: RE: ARB-704 / Tuner Port REALLY a safe alternative?
Post by: K1JHS on December 22, 2012, 04:37:20 PM
I have the ARB-704 and associated cables from MFJ to link my FT-450D to an AL-811. I have not had any issues with either and my tuner still works just fine however I hope you don't think you use the tuner with the amp on do you? The cable does not affect the inboard tuner at all if you are running 100 watts barefoot, it works as it always did.

Hope this helps.... John


Title: RE: ARB-704 / Tuner Port REALLY a safe alternative?
Post by: KB1TJY on December 22, 2012, 04:38:18 PM
Lyman, I was working at HRO and we had a similar situation today with an FT-450 and an AL-811. I think the 704 is used as a buffer between higher keying voltage amps like the SB-200 or such, so it does not blow out the keyer. Someone correct me if I am wrong. We were still trying to figure out the cable mess to see if there was a typo or mistake on Ameritron's website. But that was rather frustrating today.
Thanks. This would seem to be the case the more I read...

Lyman


Title: RE: ARB-704 / Tuner Port REALLY a safe alternative?
Post by: N4NYY on December 22, 2012, 04:39:52 PM
Lyman, I was working at HRO and we had a similar situation today with an FT-450 and an AL-811. I think the 704 is used as a buffer between higher keying voltage amps like the SB-200 or such, so it does not blow out the keyer. Someone correct me if I am wrong. We were still trying to figure out the cable mess to see if there was a typo or mistake on Ameritron's website. But that was rather frustrating today.
Thanks. This would seem to be the case the more I read...

Lyman

The ideal situation would have been for us to call Ameritron and figure this out, but they are closed on Sat, and I only work on Sat.


Title: RE: ARB-704 / Tuner Port REALLY a safe alternative?
Post by: K1JHS on December 22, 2012, 04:40:28 PM
Oh yeah and I forgot to mention it does indeed go into the tuner port.


Title: RE: ARB-704 / Tuner Port REALLY a safe alternative?
Post by: KB1TJY on December 22, 2012, 04:42:11 PM
I have the ARB-704 and associated cables from MFJ to link my FT-450D to an AL-811. I have not had any issues with either and my tuner still works just fine however I hope you don't think you use the tuner with the amp on do you? The cable does not affect the inboard tuner at all if you are running 100 watts barefoot, it works as it always did.

Hope this helps.... John
Thanks John. I put the external Amp in standby when tuning. Where did you connect the PNP-8M, into the Tuner port of the 450D and then into the ARB? I am not using ALC, btw.

I take it you are not using external power for the ARB?

Lyman
KB1TJY


Title: RE: ARB-704 / Tuner Port REALLY a safe alternative?
Post by: N4NYY on December 22, 2012, 04:42:53 PM
Oh yeah and I forgot to mention it does indeed go into the tuner port.

Great info! That is what had us confused. I will let my colleagues at HRO know.


Title: RE: ARB-704 / Tuner Port REALLY a safe alternative?
Post by: K1JHS on December 22, 2012, 04:49:43 PM
Lyman, when you tune in standby with the amp on this only applies to the tuning out to the antenna, the amp is in pass through mode. When the amp is in operate mode you actually tune the finals of the amp (poor description) to the load of the antenna. There SHOULD be no need of a tuner between the FT450 and an AL80 (or 811 in my case) as the amp has a "tuned" input to represent a less than 2:1 swr to the rig as long as the bands on both agree with each other.

Hope all of this makes sense..... J


Title: RE: ARB-704 / Tuner Port REALLY a safe alternative?
Post by: KB1TJY on December 22, 2012, 07:30:56 PM
Lyman, when you tune in standby with the amp on this only applies to the tuning out to the antenna, the amp is in pass through mode. When the amp is in operate mode you actually tune the finals of the amp (poor description) to the load of the antenna. There SHOULD be no need of a tuner between the FT450 and an AL80 (or 811 in my case) as the amp has a "tuned" input to represent a less than 2:1 swr to the rig as long as the bands on both agree with each other.

Hope all of this makes sense..... J
Thanks. So you're saying I should be using the internal Tuner with the amplifier on and NOT in standby?

Again, many thanks.


Title: RE: ARB-704 / Tuner Port REALLY a safe alternative?
Post by: TANAKASAN on December 23, 2012, 01:52:17 AM
"Yaesu charges a premium for the use of their 10-pin connector"

Please could somebody explain that bit.

Tanakasan


Title: RE: ARB-704 / Tuner Port REALLY a safe alternative?
Post by: G3RZP on December 23, 2012, 04:18:25 AM
Lyman,

If the SWR on the feed to the antenna is such that you need a tuner, then you need a suitably rated tuner between the amp and the antenna, as well as an SWR meter between amp and antenna. You can adjust that for a 1:1 SWR with the amp in standby and the internal tuner not working, just using low power from the transceiver. Then switch the amp on and tune it up to full output power.


Title: RE: ARB-704 / Tuner Port REALLY a safe alternative?
Post by: W1QJ on December 23, 2012, 05:14:57 AM
1. DO NOT have the radio's internal antenna tuner "on" when using it with the amp "in line" or "operating". 
2.  If the amp is "off" or in standby and will not amplifiy, you may use the antenna tuner in the radio to tune the antenna, but turn it off if the amp will be used in operate.
3. As said, if the antenna needs to be tuned because the swr is high or you are using a G5RV then you will need an external tuner that can handle the amplfier power.
4. If it is dertermined that you need an external antenna tuner then you would use it as the "default" tuner in all cases.
5. If you have multiple antennas then the above may be different.


Title: RE: ARB-704 / Tuner Port REALLY a safe alternative?
Post by: KB1TJY on December 23, 2012, 08:14:46 PM
Lyman,

If the SWR on the feed to the antenna is such that you need a tuner, then you need a suitably rated tuner between the amp and the antenna, as well as an SWR meter between amp and antenna. You can adjust that for a 1:1 SWR with the amp in standby and the internal tuner not working, just using low power from the transceiver. Then switch the amp on and tune it up to full output power.
Thanks!

Lyman
KB1TJY


Title: RE: ARB-704 / Tuner Port REALLY a safe alternative?
Post by: KB1TJY on December 23, 2012, 08:17:21 PM
1. DO NOT have the radio's internal antenna tuner "on" when using it with the amp "in line" or "operating". 
2.  If the amp is "off" or in standby and will not amplifiy, you may use the antenna tuner in the radio to tune the antenna, but turn it off if the amp will be used in operate.
3. As said, if the antenna needs to be tuned because the swr is high or you are using a G5RV then you will need an external tuner that can handle the amplfier power.
4. If it is dertermined that you need an external antenna tuner then you would use it as the "default" tuner in all cases.
5. If you have multiple antennas then the above may be different.
Thank you. I've a Palstar AT2K that I've used for the past nearly two years but honestly it does not seem to have any advantage over the Tuner built-in to the Rig. The latter seems to  be doing fine pulling a near 1:1.

Again, many thanks!



Title: RE: ARB-704 / Tuner Port REALLY a safe alternative?
Post by: KF7CG on December 26, 2012, 11:09:37 AM
KB1TJY,

You are missing something in the discussion. When the amplifier is in operate mode, the radio's antenna tunner only tunes out any mismatch between the radio and the amplifier. The amplifier very effectively prevents the radio tuner from seeing the antenna. This causes the swr from the amplifier to the antenna to be what it will unless there is an antenna tuner between the amplifier and the antenna.

Believe it or not, amplifier tubes are quite good at isolating the antenna impedance from the rig output. In fact they transform the 50 ohm input impedance to something like 3k to 5k and that is reduced to 50 ohms again by the amplifier output circuits if it is a tube type amplifier. For transistor amplifiers


Title: RE: ARB-704 / Tuner Port REALLY a safe alternative?
Post by: K8AC on December 27, 2012, 06:14:40 AM
If you think about what needs to be accomplished to switch the amplifier, it isn't hard to figure out.  See the diagrams on page 8 of the FT-450 manual.  To switch the amplifier, you need to ground the PTT line of the amplifier.  Both the Data and Linear jacks include a pin named: TX Gnd Out.  That line is connected to nothing else on those two connectors - it just goes to ground when the transceiver goes to transmit.  Page 13 gives the limits on the voltage and current that the switching transistor in the 450 will handle.  The safe thing to do would be to measure the voltage on the amplifier PTT line, and then measure the current as you short the PTT line to ground with the ammeter in series.  If both the current and voltage observed are within the limits of the transistor, then you don't need the 704 to protect the 450.   It's not unusual at all for a transceiver to provide the amplifier keying line on more than one rear panel connector.  If you have something else already plugged into the Tuner jack, open the connector and add a wire to the TX Gnd Out pin.

73, Floyd - K8AC


Title: RE: ARB-704 / Tuner Port REALLY a safe alternative?
Post by: KH6AQ on December 27, 2012, 06:34:48 AM
What amplifier are you using? The ARB704 is not needed with any modern amplifier than I am aware of.


Title: RE: ARB-704 / Tuner Port REALLY a safe alternative?
Post by: KC9TNH on December 27, 2012, 10:29:04 AM
What amplifier are you using? The ARB704 is not needed with any modern amplifier than I am aware of.
The Amp is an Ameritron AL-80B.

Lyman
KB1TJY
FT-450D, AL-80B (with a 17-yo Eimac  ;D) and AT2K tuner here. No buffer, no issues, no unnecessary interconnections.

- Amp tuned the way taught by W8JI and WB2WIK, settings for amp & tuner on a cheat sheet on the desk. (Thank you gentlemen for the grain from alot of old thread-chaff.)

- Have the 450D Pnl/C.S. front-panel push-button programmed for SWR function which allows a quick 10w carrier to check whatever the AT2K's  been set to w/amp in standby; takes less than a second.

- AT2K switched to a direct output to which is connected a 1.5K dummy load. Amp on, verify output to dummy load so as not to bother the folks on a band.

- Flip AT2K back to antenna selector; play radio. Takes longer to type than do.

You have a great combo, it will serve you well.
:)