Autofils,
Posting issues resulted in a misunderstanding. I quoted Jasmo's post #145, but find no quote posted with my comments.

In the absence of the quote, you could reasonably think I was commenting on mlord's SBGH or your Ottawa SBGH work. I was not. Quite the contrary, I'm very interested in what you're doing, understandably focused on the G-H approach, but perfectly valid. I look forward to your results, and will have no issues if you all stay mum until you've got something.

My only point for Jasmo was that by varying dimensions within a single antenna you get something entirely new, requiring it's own modeling for performance predictions. Scaling all dimensions of a single antenna, as it sounds you're doing with the Ottawa SBGH, remains an approach that allows performance predictions without modeling runs. Since I bet you'll do the modeling anyway, you may validate the scaling approach.

Then again, perhaps Jasmo has an idea you want to pursue. After all, it's not that different from the log-periodic approach, albeit without the feedlines.

And I would love to join you all in antenna modeling, but I don't expect to do so soon.

Sorry fo rthe misunderstanding,
Frank

And I would love to join you all in antenna modeling, but I don't expect to do so soon.

Sorry fo rthe misunderstanding,
Frank

Hi Frank,

I'm looking forward to this nerd modeling club and thanks for considering joining.
At the moment I see this working by using the pm messaging for us nerds to discuss modeling projects, exchange information and basically help
each other with modeling tips etc. Hopefully we can agree on some tasks, with defined objectives, such as optimizing feed-point gap, as a simple starter and then move on to larger tasks. We will need to make some rules about how the resulting info is presented on the forum and to save personal embarrassment (.. like some my dohs...and stupid mistakes) have the model data re-tested by another nerd before it's posted.

We could consider using Skype or similar software to allow pc to pc voice and video exchanges.

These are some ideas to get us started...I'm sure others will add to that list.

Re my posting on the Ottawa_DS, I only wanted to ensure that the basics of the design was clear.
Maybe I jumped the gun by assuming your post was in reference to that.

Our nerd modeling club could certainly reduce such mis-understandings, as we could with Stampeder's help, set up a separate thread for models. So for Jasmo's post, that suggestion would go to the nerd thread, where it would be assigned an identification name/number and evaluated by the nerds with the rules that we evolve for new design submissions.
That would keep "development topics" away from the "How do I build the current design" thread.

Well I'm rambling on far too long here...but hopefully all potential nerds get the idea.

Maybe Stampeder will assist in getting this organized and setup....It's too big a task for this nerd...I can only try to get the ball rolling...

From what I recall when fidgeting with the model dimensions, you get more effect from lengthening the horizontal extensions than you do changing the gap between the members. It occurred to me you could make those pieces with telscoping parts and do some tuning.

From what I recall when fidgeting with the model dimensions, you get more effect from lengthening the horizontal extensions than you do changing the gap between the members. It occurred to me you could make those pieces with telscoping parts and do some tuning.

vman41,

Good to hear from you and welcome to our forum.

For the benefit of regular DHC members, vman41, is the fellow that spotted the asymmetrical lobe in the SBGH data, which left me a bit red-faced on the AVS forum, once the problem was solved by old sparks. That's when I started to consider the "Nerd Club".

I haven't looked at the array spacing variations, but I have looked at the length of the array's horizontal tabs, and its good to hear that you have found similar results, that the frequency response can be tailored to some degree with a change in those lengths.
[If you still have your results for array spacing variations, could you send me a pm...Sounds like, you have already looked at that, and the current feed-gap of 44mm is good?....thanks]

Your suggestion for telescoping parts is excellent and I'm hoping that mlord's tower will become our "Official Ottawa Test-Site" to test this and future variations.

I received a DBGH nec file from Kro a while back, and he and I are currently exchanging ideas on the DBGH.
[ That just started today ..!!]
His model has an interesting variation on the phasing line that is worth further investigation. I based the phasing line spacing on the ARRL formula of about 6x wire diameter, and have not modeled any variations on the phasing line parameters.

Considering Ken Nist's comments on his web site about poor phasing line design of the CM-4228, this needs a closer look.
Quoting hdtvprimer.com
Channel Master says this is their best UHF antenna. It is probably the best overall UHF antenna available. But it is not without its faults. Since it is just two 4-Bays hooked together, one would expect its gain to be 4 dB better across the band (3 dB for being twice the antenna plus another dB for the continuous screen blocking more radiation out the back). But its special feed lines are badly designed. They radiate and are poorly matched to the line.

Here is the hdtvprimer.com link for the above CM-4228 quote.
http://www.hdtvprimer.com/ANTENNAS/cm4228.html

I really appreciate your post and the DBGH nec file from Kro.
This just might be the start of the "Nerd Club" ...we will learn as we go...
Looks like the top priority now is to examine the DBGH phasing line.

...thanks
autofils

Hi guys, a co-worker saw the recent posting on Slashdot, and asked me what I thought. I'm a self-proclaimed antenna geek, and have spent the last few days reading up on your project. If you're looking for another local Ottawa guy to help toss ideas around, share simulation results, field-test antennas, I'm here. I was active on the OTA forum about a year ago, but I haven't been checking until just recently. I've got a home-made copy of the Radio Shack Hoverman in my attic with a Radio Shack pre-amp (i.e. LOTS of room for improvement) and get WNPI-DT solid every time I've checked, as well as CBOT-DT and CBOFT-DT. WCFE-DT is mostly not there, but I'm aimed to favour Watertown in hopes of getting WVNY and WWTI (which I only get very rarely). Looking forward to participating...
Dave

I'm a self-proclaimed antenna geek, and have spent the last few days reading up on your project. If you're looking for another local Ottawa guy to help toss ideas around, share simulation results, field-test antennas, I'm here. ...
Dave

DaveM

Thanks for your interest and your posting. I am hoping to start with a core-group of guys that have some background with antenna/modeling and you are very welcome to join this journey. I'll be contacting you via the pm system.

There are a whole host of things that will need to get sorted out by this core group. Things like...

1 Membership to the Nerd Club
I think if this has any chance of success, we need to first get a core group of people that have some experience and knowledge on the subject matter. We can evolve tutorials for newcomers to this modeling world, once we have got the Nerd Club off the ground.

2. How do we communicate?
Currently I'm just using this forum's pm system, and having exchanges with Kro and vman41
It might be easier for the core-group members ( >10?) to use Skype or similar pc to pc calling and establish conference calls.

3. nec files ( Repository, filesystem - Naming conventions, version control, - common modeling rules...and the list keeps going

3. Setting Modeling Objectives
Currently, my view is the phasing line optimization of the DBGH has top priority. What about other GH tasks? What about future configurations, GH and other antenna types ..downshifted CM-4228?

4. Your choice !! Add one...or two..or ...

Maybe, just maybe, we can become the hardware Antenna Modeling equivalent of open source Linux ???
There are likely more improvements to be made with the GH, and other antenna types using this modeling approach...only more modeling runs will tell ! But the journey will be very interesting !!!!