Hi Guys,
just built a minikits 2.4G transverter, with a 23cm on the way... How do people manage the PTT activation for SSB on this rig?? There is a PTT input on the Data port, but doesn't seem to be a PTT out anywhere??
cheers,
Dan VK2GG
FT 817 as IF FOR TRANSVERTERS
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VK3HZ
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Re: FT 817 as IF FOR TRANSVERTERS
IMHO, just about the best IF rig for portable ops.
Have a look down the bottom of this page for how I did it: http://home.exetel.com.au/dwsmith/
Regards,
Dave.
Have a look down the bottom of this page for how I did it: http://home.exetel.com.au/dwsmith/
Regards,
Dave.
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VK1BL
Re: FT 817 as IF FOR TRANSVERTERS
I use a separate PTT line between the IF rig and the transverter, not elegent by any means but it works. I'd prefer to send a DC voltage along the IF coax to the transverter and think that's a sensible scheme for all my transverters, just have to implement it... 
BTW Matt, we'll have 13cm running form Mt Coree this Spring FD. 25W to a 1.2m dish so a QSO with you is possible, I've worked Adrian 2FZ in Balmain from Mt Coree previously, so it's possible... you may need to up the power from your Mini-kits transverter - get to it!
73, Ted - VK1BL
BTW Matt, we'll have 13cm running form Mt Coree this Spring FD. 25W to a 1.2m dish so a QSO with you is possible, I've worked Adrian 2FZ in Balmain from Mt Coree previously, so it's possible... you may need to up the power from your Mini-kits transverter - get to it!
73, Ted - VK1BL
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VK3BJM
Re: FT 817 as IF FOR TRANSVERTERS
Okay chaps - I've seen and heard regular comments about not using rigs like the FT847 and the IC706 for IF drivers, on account of the power spikes they produce when the output power has been "wound down". The FT817 hasn't the same level of high power grunt, but will it produce spikes if "wound down" from the normal full 5 watt output?
My intention to use one of these rigs with my transverters has paused momentarily, as all are fitted with VK5EME sequencers, supposedly rated at 3 watts maximum from the IF driver. 2 dB isn't much of a difference, but I don't want some component to fail, triggering a larger event, just as that critical long-haul contact is nearly complete. As it would...
Modifying the sequencers, with higher rated resistors in the IF input, obviously bypasses such concerns; but I have half a dozen of these things (sequencers), so there is a degree of faffing around that I'd prefer to avoid if possible.
73,
Barry
VK3BJM
My intention to use one of these rigs with my transverters has paused momentarily, as all are fitted with VK5EME sequencers, supposedly rated at 3 watts maximum from the IF driver. 2 dB isn't much of a difference, but I don't want some component to fail, triggering a larger event, just as that critical long-haul contact is nearly complete. As it would...
Modifying the sequencers, with higher rated resistors in the IF input, obviously bypasses such concerns; but I have half a dozen of these things (sequencers), so there is a degree of faffing around that I'd prefer to avoid if possible.
73,
Barry
VK3BJM
Re: FT 817 as IF FOR TRANSVERTERS
Barry,
Interesting dilema. I have grappled with these questions before, and interestingly now I have some decent test gear to check your question, I have not done it. However, here is what I believe:
a. Mark 5EME does advise the resistor network is fine for 5 watts SSB (due to lower duty cycle).
B. even if this were not the case, if you were on lowest power for you FT7817 (0.5 watts), and you did get a spike, it would only be a transient, for a fraction of a second. Thie resistor network of 3 watts should have no problems disappating this.
It then comes down to your transvertes design, and wether it will be upset at a 10db increase in IF for a short time, from the sniffed input.
I personally have been using an FT815 on lowest power (0.5w) into a 5EME sequencer in my 2.4GHz t/verter for about 6 months with no problems. Just recently had the sequencer open and no sign of excess heating of the resistors. I guess the proof is in the pudding.
Incidentally, i recently asked mark 5EME about the suitability of this sequencer for 432 MHz IF. He has had experience with it at thisfrequency and advised it worked without problems. I am currently building one to test it at this IF as plan to put the 10GHz gear I am building on 432MHz IF. Will keep you posted.
And I will take the time overthe next few weeksto check if the FT817 does spike on low power.
Michael
VK3KH
Interesting dilema. I have grappled with these questions before, and interestingly now I have some decent test gear to check your question, I have not done it. However, here is what I believe:
a. Mark 5EME does advise the resistor network is fine for 5 watts SSB (due to lower duty cycle).
B. even if this were not the case, if you were on lowest power for you FT7817 (0.5 watts), and you did get a spike, it would only be a transient, for a fraction of a second. Thie resistor network of 3 watts should have no problems disappating this.
It then comes down to your transvertes design, and wether it will be upset at a 10db increase in IF for a short time, from the sniffed input.
I personally have been using an FT815 on lowest power (0.5w) into a 5EME sequencer in my 2.4GHz t/verter for about 6 months with no problems. Just recently had the sequencer open and no sign of excess heating of the resistors. I guess the proof is in the pudding.
Incidentally, i recently asked mark 5EME about the suitability of this sequencer for 432 MHz IF. He has had experience with it at thisfrequency and advised it worked without problems. I am currently building one to test it at this IF as plan to put the 10GHz gear I am building on 432MHz IF. Will keep you posted.
And I will take the time overthe next few weeksto check if the FT817 does spike on low power.
Michael
VK3KH
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VK3BJM
Re: FT 817 as IF for Transverters
Thanks Michael - I don't have gear to check this and it would be interesting to know for sure what the situation is.
The transverters I have are all set up for interfacing with my FT290r Mk1 - taking 2.5 watts. If I run the FT817 at 2.5 watts, spikes might only be 3 dB - maybe... But that's speculative, not real world and measured!
Cheers,
Barry
VK3BJM
The transverters I have are all set up for interfacing with my FT290r Mk1 - taking 2.5 watts. If I run the FT817 at 2.5 watts, spikes might only be 3 dB - maybe... But that's speculative, not real world and measured!
Cheers,
Barry
VK3BJM
Re: FT 817 as IF FOR TRANSVERTERS
Michael,
the 5EME sequencer works ok with 432 IF. I have one in my Mitec 10Ghz transverter. (Currently having problems getting the lo 8 X multiplier to work on 2 of my mitec's.) The 817 is an ideal IF Rig, as many have said. I run a separate PTT line from the acc port of the 817 to the sequencer for SSB.
cheers,
Dan vk2gg
the 5EME sequencer works ok with 432 IF. I have one in my Mitec 10Ghz transverter. (Currently having problems getting the lo 8 X multiplier to work on 2 of my mitec's.) The 817 is an ideal IF Rig, as many have said. I run a separate PTT line from the acc port of the 817 to the sequencer for SSB.
cheers,
Dan vk2gg
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VK3HZ
- Forum Diehard
- Posts: 436
- Joined: Sat Apr 02, 2005 4:52 pm
- Location: Melbourne, Australia
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Re: FT 817 as IF FOR TRANSVERTERS
Output power transient spikes would only be of concern when you have an IF rig capable of high power - FT847, IC706, TS2K etc. Down the page on the following link, there's a table that shows measurements on an IC706MkIIG where it generates spikes of up to 120W on 144MHz - http://www.nitehawk.com/sm5bsz/dynrange ... bus205.htm
The main concern with spikes is not the terminating load, but the Tx mixer (often also used as the Rx mixer) in the transverter. The resistors in the load would have to be significantly overloaded for an extended period before they'd show any blackening.
I've used an 817 for several years to drive several different transverters and have only once had a problem - due to my own stupidity
. I drove the 10GHz transverter with 5W instead of 0.5W (I now have a label to remind me to set the power to Low!) It worked OK for a while, until I ran an extended carrier after which it then no longer worked OK ... Fortunately, I had a replacement mixer in the junk pile.
So, use that 817. If it has spikes, it's probably no worse than the 290R. And in useability terms, it's streets ahead.
Regards,
Dave.
The main concern with spikes is not the terminating load, but the Tx mixer (often also used as the Rx mixer) in the transverter. The resistors in the load would have to be significantly overloaded for an extended period before they'd show any blackening.
I've used an 817 for several years to drive several different transverters and have only once had a problem - due to my own stupidity
. I drove the 10GHz transverter with 5W instead of 0.5W (I now have a label to remind me to set the power to Low!) It worked OK for a while, until I ran an extended carrier after which it then no longer worked OK ... Fortunately, I had a replacement mixer in the junk pile.So, use that 817. If it has spikes, it's probably no worse than the 290R. And in useability terms, it's streets ahead.
Regards,
Dave.
Re: FT 817 as IF FOR TRANSVERTERS
Hi Guys,
I've recently tried the TX/RX mod to the Rear SO-239 of my 817. The mod is on a link from Kuhne's site and credit goes to Petro ON7WP for the design.
Two things worry me: The +3V DC does seem to be sufficient for switching a Kuhne Transverter, but may be inadequate for MiniKits and other transverters. The second worry is that the 70cm power output has dropped to some 30mW - ok for minimal power from my 10G Kuhne transverter, but not sufficient for maximum power of 2.5/3W out from my DEMI PA. I have solved the problem with a manual PTT - but not as elegant as a thru-coax solution. Has anyone else tried this mod?
Dan
I've recently tried the TX/RX mod to the Rear SO-239 of my 817. The mod is on a link from Kuhne's site and credit goes to Petro ON7WP for the design.
Two things worry me: The +3V DC does seem to be sufficient for switching a Kuhne Transverter, but may be inadequate for MiniKits and other transverters. The second worry is that the 70cm power output has dropped to some 30mW - ok for minimal power from my 10G Kuhne transverter, but not sufficient for maximum power of 2.5/3W out from my DEMI PA. I have solved the problem with a manual PTT - but not as elegant as a thru-coax solution. Has anyone else tried this mod?
Dan
Re: FT 817 as IF FOR TRANSVERTERS
Dan, there is something very, very wrong if the FT-817's output power on 70cm drops to 30mW after this mod (http://www.kuhne-electronic.de/en/32_Pr ... /154_AN005). The mod looks pretty sound to me. I've not done it to my FT-817, but I've installed similar mods to a variety of rigs including IC-202's, Kenwood TR-751A's etc. without problems. I'd advise checking the chip caps in case they suffered damage during installation.
With the Ft-817 I use a home-brew external bias-T which is activated from the rig's accessory connector and feeds +Vdc up the coax. I thought about modding the rig internally but it's just too much of a squeeze around the SO-239.
I've made it a practice to arrange all my microwave transverters to accept 2.5W of drive on TX. That way I can use my FT-817, FT-290RMk1 or IC-202 interchangeably and without risk of damage, even if my brain fails and I hit them with 5W. While the ALC action of the FT-817 is pretty terrible, its power "overshoot" is simply not enough to do any damage (Barry is on the right track here).
I would never contemplate using an IC-706 (any flavour) or FT-857/897 with the power wound down as a transverter driver. I have performed actual measuremets which confirm David VK3HZ's remarks.
Chas
VK3PY
With the Ft-817 I use a home-brew external bias-T which is activated from the rig's accessory connector and feeds +Vdc up the coax. I thought about modding the rig internally but it's just too much of a squeeze around the SO-239.
I've made it a practice to arrange all my microwave transverters to accept 2.5W of drive on TX. That way I can use my FT-817, FT-290RMk1 or IC-202 interchangeably and without risk of damage, even if my brain fails and I hit them with 5W. While the ALC action of the FT-817 is pretty terrible, its power "overshoot" is simply not enough to do any damage (Barry is on the right track here).
I would never contemplate using an IC-706 (any flavour) or FT-857/897 with the power wound down as a transverter driver. I have performed actual measuremets which confirm David VK3HZ's remarks.
Chas
VK3PY