A search of the reflector didn’t return any results so here comes a question:
I normally use the front antenna on my FT817 whilst out SOTA’ing but I’ve recently read somewhere on the net (nb: I can’t find the post again!) that the rear antenna should be used instead of the front as it doesn’t ‘energise the relay’ and lessens the wear on said relay. Is this correct? Should I be using the rear antenna? Comments / thoughts / wisdom are all welcome.
73, Lea M0XPO
No, use the front antenna:
I have a Satan-to-BNC adaptor on the rear connector. To swap between 2m antenna and the 1296 transverter I use the config menu number 08 to swap between front and rear, effectively a band switch. But the power level also has to be changed as I have set the transverter to use 1w drive from the 817.
As the rx consumption is over 400ma I tend not to worry about the extra 20 ma and use whatever connector I want to.
73 Andrew VK1DA/VK2DA
PS. There is a FT817 group on groups.io. If you join that and use the search tool on groups.io, you’ll find someone’s report on current consumption of the 817. Quite illuminating.
Andrew,
Thanks…… group now joined!
Here’s a controversial opinion that I’m not going to sit on the fence about.
Use whichever connector that is most convenient for your particular set-up 
Carolyn
Hi Carolyn,
I agree. 20mA is so little compared with 400ma the rig draws anyway. It’s not worth worrying about.
73 Andrew VK1DA/VK2DA
They can be convenient, though. I have a right-angle adapter on mine which allows me to use a mobile half-wave 2m whip if I can’t be bothered to put something on a mast.
Hi Lea,
I have noticed some differences between the two connectors. The main one being that measured SWR for a particular antenna is different (up to two bars different on the radio SWR meter) between the two connectors. I also found odd behaviour when using a 2m TX-sense amplifier between the BNC and SO-239 connector; it sometimes clicked on/off very quickly, rather than staying on TX when talking. Fixed by using a wired PTT connection. Maybe my radio was a Friday afternoon job…? 
Generally I use the SO-239 for HF as that’s what I have on the dipoles and, I use the BNC for 2m/70cm as that’s what I have on the SlimJim. Usually works fine for me and Nic. I’m not sure about wearing out the relay - dropping it off a rock or into a Welsh bog is a more likely risk for us…
73, Simon
I would agree with FMF’s advice for correctness, but would also offer my thoughts.
Use whatever connector suits your equipment
Similar to VK Andrew I use both connectors at the same time and switch between transverters with different I.F.s by using the bandswitch.
The front connector is more fragile than the rear. Both of my 817’s have had the BNC come lose and required some small dismantling of the radio to re-tighten the connector mounting nut.
Stuart - G1ZAR/P
The relay in my ~21-year-old FT817 is still working fine nor I have read any problems from other FT817 users. I wouldn’t worry about that possibility: I use the antenna socket that suits the antenna I’m using at the time.
I find using the front (BNC) socket a nuisance when wanting to adjust the LHS controls and [like others] sometimes use a PL259-BNC adapter on the rear socket especially an L-shaped one so I can have my RH770 2m 1/2-wave telescopic with the FT817 lying flat.
Actually, toggling the Rear/Front Antenna menu option is a very quick and convenient way to do a A vs B comparison on two antennas.
I’ve standardised on BNC but I don’t use the front BNC on my FT817, I use an adapter on the rear socket as I find it more convenient.
When I first got my 817 I used the front BNC connector, but it is definitely more fragile than the rear SO-239, so I stopped using it well over a decade ago. My set up uses flying leads to remove the strain on the rig’s connectors, so the system has a PL-259 to bulkhead BNC lead. I really ought to change over to TNCs for RF, but that’s a time and expense exercise.
I had problems with bnc on my ft818. Also, find another 818 with same problem. Ralay is bad. Rear connector works fine
I am using rear connector for hf and bnc for 6m/2m/70cm. Changing bands switching is automatic
You are probably in more danger of damaging your rig by forgetting which connector is enabled in the menu and hook the antenna up to the wrong antenna socket. I am guilty of that and thankfully the radio survived my once off indiscretion. For that reason I now only have BNC type fittings on my portable antennas, its vary rare I have a PL 259 type portable antenna feed line for my FT817 so I keep front socket enabled in menu.
Regards
Ian vk5cz…