开云体育

How do you prevent damage from a lightning event if everything is not referenced to one ground (earthing point)?
The potential difference between the two, or more, earth points can be very substantial.
This potential difference is what causes the damage.

Glenn

In UK the "house" ground is usually connected "earth" and connected to neutral at the substation (transformer for the locality). In Ireland there is supposed to be a 1.5m approx galvanised earth spike near the meter box or grid input and the neutral and earth are bonded there. That's quieter.

Maybe 50 years ago people might have used the water pipe as an RF earth, but that might be plastic. You're not supposed to use any utility pipes, central heating pipes etc as a radio Earth.

Don't connect your own Earth spike to the mains supply Earth. They need isolated, especially on the UK system as large currents might flow. The exception might be if your neutral and earth are bonded at the meter box and go to a nearby earth spike and there is no utility company earth.

Every non-loop aerial has a "counterpoise" even if you can't see it. A vertical needs either to be driven at earth level, or have 1/4 wave or more radials or counterpoise, or a sleeve that is earthed only at drive point with an internal diameter ratio with coax outer diameter to give the 50 or 75 Ohms. An unfolded, non-loop, dipole obviously has a "counterpoise".

The end fed Zepp (so called because used on the Zeppelins as a radio aerial) doesn't seem to have a counterpoise, but has really, on the modern version the feed line is the counterpoise. Similarly the over hyped G5RV is only a proper dipole at one narrow band, otherwise the feed cable is the aerial (and partly counterpoise) and then the counterpoise is really the shack earth.

The thing to avoid is an exactly half-wave radiator or counterpoise as that has a very high impedance.

-- 
-----------------------------------------------------------------------
Glenn Little                ARRL Technical Specialist   QCWA  LM 28417
Amateur Callsign:  WB4UIV            wb4uiv@...    AMSAT LM 2178
QTH:  Goose Creek, SC USA (EM92xx)  USSVI, FRA, NRA-LM    ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"

In UK the "house" ground is usually connected "earth" and connected to neutral at the substation (transformer for the locality). In Ireland there is supposed to be a 1.5m approx galvanised earth spike near the meter box or grid input and the neutral and earth are bonded there. That's quieter.

Maybe 50 years ago people might have used the water pipe as an RF earth, but that might be plastic. You're not supposed to use any utility pipes, central heating pipes etc as a radio Earth.

Don't connect your own Earth spike to the mains supply Earth. They need isolated, especially on the UK system as large currents might flow. The exception might be if your neutral and earth are bonded at the meter box and go to a nearby earth spike and there is no utility company earth.

Every non-loop aerial has a "counterpoise" even if you can't see it. A vertical needs either to be driven at earth level, or have 1/4 wave or more radials or counterpoise, or a sleeve that is earthed only at drive point with an internal diameter ratio with coax outer diameter to give the 50 or 75 Ohms. An unfolded, non-loop, dipole obviously has a "counterpoise".

The end fed Zepp (so called because used on the Zeppelins as a radio aerial) doesn't seem to have a counterpoise, but has really, on the modern version the feed line is the counterpoise. Similarly the over hyped G5RV is only a proper dipole at one narrow band, otherwise the feed cable is the aerial (and partly counterpoise) and then the counterpoise is really the shack earth.

The thing to avoid is an exactly half-wave radiator or counterpoise as that has a very high impedance.

hi folks
got a new
Panel Unit - ETCS2518403
Main Unit - CP6778033
PA Unit - CB1152002
it works!
Ok, I try out short wave first and FM radio - 2m and 70cm should work also...
I still have to install the final unit. This is not difficult. Alignment will be according to the service manual.
In sum: it is a brand new FT-81* in an old frame *big smile*
cheers for now - Ray, DL1EGR

please check

for more details...

Am 08.11.2024 um 13:53 schrieb ly5ez via groups.io:

开云体育

Hi

Just a thought, the calibration data is contained in the control head and so by changing the main board this may now be invalid, might be worth going through the calibration process..

Got Main Unit, PA Unit.?
Put them in the FT-817 shell. Rewirering was very easy. First power-up let the display blink in 1sec. interval, no audio (ex. 160m). Current as usual...?
?[F] & [V/M] & power on - sequence on #1 start... frustrating...
Today a FT818 Display Unit comes in. Will replace the FT817 Display Unit by this and hope....
cheer for now - Ray, DL1EGR

Recent subscriber, expect to have enough time to get a grip on my 817ND now, and thankful for the resource.

73

开云体育

开云体育