[IRCA] A simple Phased BOG System description and a recent mod

["Neil Kazaross" <neilkaz@xxxxxxxxxxxxx>]

A couple DXers have asked about phasing BOGs so I'll spend some time 
describing what I do with BOGs. First of all, I strive to get my BOGs close 
to the ground..ie across low cut grass, on dirt or mulch, or on my driveway. 
I want to take advantage of the fact that the velocity factor is lower when 
the wires are very close to ground to hopefully give me an antenna with 
similar directivity to an elevated Bev. The field to the east of my house 
here in IL is about 85% the size of a football field and nearly as flat as 
one and low cut. If one is going thru areas with under growth or tall 
grasses I have found that the quickest way to get the wire close to ground 
is then to roll the spool on the ground and then walk back and forth and try 
to get the wire lower and step on it. I strongly recommend cord winders for 
BOG wire as they make it easy to install and supereasy to pickup. These 
things cost about $7 at Home Depot or Lowes.

The simplest Phased BOG System and one that is very easy to use will likely 
result in many new mid and high band loggings for most domestic DXers due to 
both a fine back null and good forward directivity. First of all, I usually 
DX out of my truck and I use the quantum phaser and battery pack. Other 
phasers should also work so feel free to test or home brew your own. I 
usually don't use transformers (a presumed 5:1 SWR doesn't seem to hurt)and 
cables when DXing in my truck but simply run the wire ends under the truck 
door(s) and hook up to the phaser on the passenger seat. Simple isn't it.. 
very simple I think and very easy when I need to break the setup down as 
well as quick and easy to setup. Yes..no transformers, no cables (except 
from the phaser to rx) and I am inputting the medium impedance BOGs (about 
250 ohms) directly into the 50 ohm phaser inputs. I am breaking some RF 
rules..but so what ? It doesn't hurt performance for mini-DXpeds in my 
fields and it means that setup and take down take about 10 minutes.

I will describe the 320 deg Phased BOG System I have been recently using 
here in IL since pwerline qrn mostly went away earlier in the year, allowing 
me to park at the SE end of my field and have no noise sometimes. The main 
wire runs from under my truck door and slopes down to ground and has a total 
length of 330 ft. It is straight as an arrow aimed about 320 deg. I want 
these short BOGs very straight to try to narrow the beamwidth as much as 
possible, but the concept will still work fine with some small bends. The 
second wire run out under the same truck door and is 200 ft long. The wires 
are very close together when they enter my DX truck and pass under my legs 
and then hook up to the phaser. This doesn't seem to harm performance one 
bit and I have also come in under the passenger door and hooked up and it 
works the same. The wires are // and seperated by about 1.5 feet. That 
distance apart isn't critical and I've used them 1 feet apart or 3 feet aprt 
and the Phased BOG System is jasu as effective them as now. When I reach the 
lengths I want for these quicky setups I just leave the spool of wire on the 
ground and this doesn't hurt performance either.

130 feet difference in length seems to work well for the upper part of the 
AM band. If you have the wires the same length you'll phase null everything 
deeply. If you make the shorter wire too short, its beamwidth widens more 
than I'd like. Longer BOGs would be more effective for the lower end but I 
have no more room here towards the NW. When I use longer BOGs to the ENE in 
WI for mid latitude TA's and SSS to New England and NY State. I tend to use 
about 180 or 190 feet difference in length. (This seemed good when I got 
Ireland on 549 in WI and has also made me think that I was DXing from Spain 
with them all over the dial. Last time in WI I used 415 ft // 281 ft aimed 
more northerly and while I'd like longer wires for the lower end, getting 
Syria, Spain, and Mauritania on 783 passed phased back end WBBM (92 miles) 
would indicate a decent antenna system. The exact lengths of BOGs for the 
Phased BOG System isn't critical and I don't feel that the difference in 
lengths is critical either. You want to make sure that the DX left over when 
you phase the back end isn't greatly attenuated and most certainly you don't 
want it attenuated across the band. The low end here with my setup in IL 
seems rather attenuated but getting CKUA 580 indicates that it can still 
provide nice DX.

Use: OK so you have your two // BOGs down and it is time to phase them to 
null back end pests. Compare back end amplitudes and they are usually 
similar but make whatever quick adjustment it needed to get them close to 
equal and then adjust phase as needed to null more and back and forth 
tweaking amplitude and phase until you greatly reduce that back end pest. 
The nulls are reasonably broadbanded and decently wide. Phasing WRTO 1200 is 
good for much of the upper band while phasing WLAC 1510 tends to require a 
bit different phaser tweaking and is good for the very high band. Phasing 
WMVP 1000 seems good for midband. WMVP is SE of here but the null of it also 
reduces things like KDKA and WBZ and KYW to the east enough to tell there's 
stuff under but I may sometimes want to further deepend that specific null.

The array can also be used to null stuff in the direction it points but even 
at these lengths BOGs have a few dB of attenuation and it is preferable to 
aim directly at the DX. That being said, two years ago and a few times in AU 
cx the back ends of my Phased TA BOGs provided a pipeline to Veracruz.

Termination: Note that this quicky Phased BOG System requires no 
termination. I seriously don't recommend putting ground rods on land you 
don't own ! Termination can help further reduce back end qrm, but I've never 
seen it do a good job across the entire BCB band (also not seen that for 
classic elevated Bevs). I also have not found that fanning out a few wires 
on the ground after the resistor rather than using a ground rod did anything 
to help BOG termination. I suspect they simply may become part of the 
antenna. However, this is reported to work at LBI, but beach sand 
conductivity is likely much less than my midwestern soil.  More on 
termination in a later post, but for quick use and casual use don't worry 
about it ! Just phase a pair of different length // BOGs and enjoy.

A recent mod seems quite useful for the upper band. I strongly believe that 
the best performance and most broadbanded nulls (ie for Perseus users to 
record the entire band) would be obtained from // staggered BOGs or Bevs the 
same length. Theoretically with feedpoints 1/4 wave apart and 90 degrees 
phase different would result in adding in phase in one direction while 
having a nice 180 deg out of phase null for the other. If you combine the 
two antennas 180 deg out of phase and then use either delay line or a LC 
circuit the back end should be 180 deg out of phase for the entire band. 1/8 
wave apart and 3/8 wave phasing would also work, of course.

With that in mind, and wanting to use a longer phase shorter BOG to narrow 
its beam a bit, I decided to try extending the back end of the shorter BOG 
and then bending it back to my DX truck and phaser. So now while my 330 ft 
BOG at 320 deg remains the same, the shorter wire still runs 200 ft to my 
truck but passes under it and goes 51.5 feet (I haven't an inch more room) 
and then bends 180 degrees and comes back to my DX truck and hooks up to the 
phaser. This is somewhat staggering two BOGs and seems to have more signal 
left over when I phase the back end pests. The doublebacked BOG usually has 
a bit more backend pest signal than my longer straight one so I just need to 
add a bit of resistance with that phaser pot. It really seems that I have 
more signal left over after phase nulling now across the band and especially 
across the high end. When I phase null to the Palatine TIS on 1660 due SE, 
WTDY due NW on 1670 isn't any weaker on the phased combo than on a single 
wire and some upper band stuff is honestly a bit stronger on the pair.The 
back null also seems to be somewhat more broadbanded now !  This is exactly 
the effect that I want and a few dB can make all the difference in pulling 
out DX from the mess and pulling out that DX under a phased powerhouse 
local.  I'll make a more exhaustive test of this concept in WI where I have 
more room and where I don't have Chicago's pests to make a mess of daytime 
DX that direction. I honestly have never had some of the northwesterly DX as 
good as the past two nights.

73 KAZ

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