dave wrote:

garthpdm wrote:

Hi,

I am wondering what limitations are on the length of the ground wire
lead from the transformer/balun to the ground rod? Thanks,

Garth


There is no requirement to to ground the BalUn (UnUn) directly. The
antenna lead (coaxial cable outer conductor) must be grounded at the
point where it enters the building. That is where the main ground
should be.

In cases of high ambient noise, such as at my QTH, the following approach
taken from "Broadband Receiving Antenna Matching, Mark Connelly, WA1ION
– 15 July, 2003" has worked for me; at this time I do NOT ground the feedline
coax at any point, instead it is buried in plastic conduit at a depth of
3 feet for a distance of thirty feet (from the shack to the antenna mast),
and the balun's ground wire is only six feet in length (the balun is
in a waterproof box at the feed end of the longwire, which is configured
'Marconi'-style with a short sloped section to the mast insulator.

I use a quadrifilar winding as described he

30.5 m (100 ft.) end-fed horizontal longwire, about 1.5 m off ground
Preferred broadband match = 9:1 transformer
This is the “plain vanilla” antenna used by many DXers. It will work connected straight to a
receiver’s input, but quite a bit more signal can be squeezed out of it if it is matched correctly. In
a narrowband sense, you’d use L-C tuning. For efficient broadband coupling, a 9:1 transformer
does best. In this case we’re talking about an FT114-J with a 7 turn trifilar winding, rather than
the mediocre Mini-Circuits T9-1. Lead 1A goes to the antenna, 1B and 2A are joined, 50-ohm
output is at joined 2B and 3A leads, and common ground goes to 3B. If “station” and “field”
grounds are to be separated for noise reduction, you’ll need a quadrifilar winding with the fourth
winding feeding the coaxial line. There would be no connection at the 2B/3A junction and lead
3B would go to the field-site ground rod system. Opposite side windings (e.g. FT114-J: 21 turns
/ 7 turns or FT140-43: 33 turns / 11 turns) could also work, but sensitivity above 5 MHz may
suffer. A binocular core approach would be a 9-turn antenna winding and a 3-turn winding to
feed the coaxial cable.


Michael