[jrmclean]

stampeder mentioned in another thread that folks may be interested in pictures and measurements of a Delhi 5Y6S single channel antenna?

I've got some pictures and some measurements (cm) of the antenna.

This is the antenna spread out on my floor

My crude drawing with measurements..

Other pictures are found in my album here

Boom length is 84cm from tip to tip.

 

[ScaryBob]

Thanks for the info. Where did you get this antenna?

 

[jrmclean]

roger1818 found a distributor in the US that had some Delhi stock left....

 

[300ohm]

I take it thats a 1 inch (25.4 mm) boom, and the dimensions for the reflector/directors are from the tips to the 1" boom, but not including the 1" boom. Correct ?

A question here. The bottom piece is electrically connected across, is the middle piece also electrically connected across ?
(It looks like)
And on the top piece, whats the distance thats not electrically connected ?
And the center to center distance of the terminals ?

And are the other distances measured center of wire (tube) to center of wire (tube) ?

 

[jrmclean]

Yes, at 2.5cm, I'd say it's a 1" boom. The length of the directors/reflectors was from tip to the side of the boom. The distance between reflectors was from the mid point of the reflector to the mid point of the next reflector. The reflector elements were about 1 cm in diameter.

 

[jrmclean]

I take it thats a 1 inch (25.4 mm) boom, and the dimensions for the reflector/directors are from the tips to the 1" boom, but not including the 1" boom. Correct ?

Yes

A question here. The bottom piece is electrically connected across, is the middle piece also electrically connected across ?
(It looks like)

Yes, the middle pieces are connected electrically.

And on the top piece, whats the distance thats not electrically connected ?

I'd say about 40mm.

And the center to center distance of the terminals ?

I measured 58mm.

And are the other distances measured center of wire (tube) to center of wire (tube) ?

Yes...and the tubes are 10mm in diameter(width)

 

[stampeder]

That folded dipole design with the central bar is classic Delhi. Thanks for the photos and the diagrams!

 

[300ohm]

Reminds me why I dont like to model Vhf-Lo antennas, too many segmentation warnings to correct, heh.

Overall, it looks like a very nice 9.17 dBi Raw Gain with a SWR of 1.82 at 85 mhz.
About the highest gain antenna for channel 6 Ive seen.

Very tight usable range of from 79 mhz to 89 mhz. For FM, which is right next to channel 6, its going to be fairly poor. And channel 5 would probably be OK, but maybe iffy.

Boom length is 84cm from tip to tip.

You mean 184 cm. Its 177.5 cm not counting the end tips.

 

[jrmclean]

my oops....184cm is correct...typo transcribing from my scratch pad..

 

[tvlurker]

R
Very tight usable range of from 79 mhz to 89 mhz. For FM, which is right next to channel 6, its going to be fairly poor. And channel 5 would probably be OK, but maybe iffy.

That's good to know -- Roger1818 and jrmclean are in Ottawa, and they'll be using the antenna for 3.6 kW channel 6 digital transmitter low on a tower in a market that already has 22 FM stations that ruin reception on the existing channel 6 analog signal.

 

[300ohm]

and they'll be using the antenna for 3.6 kW channel 6 digital transmitter low on a tower in a market that already has 22 FM stations that ruin reception on the existing channel 6 analog signal.

Whats the lowest strong FM station for them in mhz ?

Another solution are filters from Tinn Lee. And hopefully the strong FM stations arent directly in their path to channel 6.

FWIW, the Delhi 5 also looks to have some decent usable gains in the 238 - 258 mhz region.

 

[tvlurker]

About 30 local stations. The lowest high power stations are the CBC at 90.7 and 91.5 MHz with 84 kW each.
Next comes 89.9 with 27 kW.
Then 89.1 with 18 kW peak.
Then 88.5 with 12 kW peak.
89.1, 89.9, 94.5 and 93.1 broadcast from the same antenna as channel 6.
According to the IC database, 88.5 is slightly lower on the tower.

call	freq	class	erpvav	erpvpk	erphav	erphpk	lat	long
cbof-fm	90.7	c1	84000	84000	84000	84000	453011	755101
cbo-fm	91.5	c1	84000	84000	84000	84000	453011	755101
cboq-fm	103.3	c1	84000	84000	84000	84000	453011	755101
cbox-fm	102.5	c1	84000	84000	84000	84000	453011	755101
chez-fm	106.1	c1	100000	100000	100000	100000	453011	755101
chri-fm	99.1	c1	25300	66000	25300	66000	451301	753350
chuo-fm	89.1	c1	3200	18100	3200	18100	453011	755101
cidg-fm	101.9	a	934	4500	934	4500	452648	753727
cidgfm*	101.9	a	1793	5500	1793	5500	452648	753727
ciht-fm	89.9	c1	27000	27000	27000	27000	453011	755101
ciif-fm	97.5	lp	34	34	0	0	452212	754215
ciio-fm	99.7	lp	25	25	25	25	452212	754211
ciiofm*	96.1	lp	25	25	0	0	452210	754215
cilv-fm	88.5	b	2300	12000	2300	12000	453011	755101
ciss-fm	105.3	c1	84000	84000	84000	84000	453011	755101
cjfo-fm	94.5	b1	2000	2000	2000	2000	453011	755101
CIMF-FM	94.9	C1	84000	84000	84000	84000	453011	755101
cjll-fm	97.9	b1	6770	6770	6770	6770	452509	754218
cjmj-fm	100.3	c1	100000	100000	100000	100000	453011	755101
cjot-fm	99.7	c1	38000	100000	38000	100000	451301	753350
cjwl-fm	98.5	a	1100	2500	1100	2500	452500	754211
ckavfm9	95.7	b1	9100	9100	9100	9100	452509	754218
ckcu-fm	93.1	b	12000	12000	12000	12000	453011	755101
ckdj-fm	107.9	a1	100	100	100	100	452100	754529
ckkl-fm	93.9	c1	95000	95000	95000	95000	453011	755101
CFTX-FM	96.5	A	1750	1750	1750	1750	452634	754358
CJRC-FM	104.7	C1	31000	100000	31000	100000	453057	753929
CKTF-FM	104.1	C1	19000	19000	19000	19000	453011	755101
ckqb-fm	106.9	c1	84000	84000	84000	84000	453011	755101
CJET-FM	92.3	B	0	0	9300	17000	450450	760552
CKBY-FM	101.1	C1	100000	100000	100000	100000	450450	760552

 

[300ohm]

At 90.7 mhz, the gain is 7.19 dBi with an SWR of 22.3, so the Net Gain is going to be less than 0. However, in some cases the Raw Gain could be a more important factor.

88.5 mhz may be a problem with still having a 9.52 dBi gain and SWR of 3.76 for a Net Gain of about 7.9 dBi.

Without a doubt, this antenna was designed for a extremely sharp cut off after channel 6, but in their cases, it may still not be sharp enough.

 

[ProjectSHO89]

Keep in mind that many FM stations transmit at up to 100 kW ERP. Even with flat to negative antenna gain in the FM band, the actual power level of the FM signal at the receiver terminals is often substantial. Commercial FM traps help, but preserving a channel 6 signal while simultaneously rejecting FM signals is quite the challenge (understatement!).

 

[300ohm]

Yep. I still have a real channel 6 (22.3 NM) and a 50 KW FM station on 94.7 mhz (-.3 dBm) just 1.2 miles away. Im lucky though it falls in the null zone for my channel 6. Someone just 3 miles to my southwest would have real problems getting that channel, heh.

 

[stampeder]

Bring It Back From The Dead, Please!

For DIYers this out-of-production Delhi 5Y6S antenna looks to be about the best channel 6 model to attempt to clone.

To summarize the findings, jrmclean's Delhi 5Y6S channel-cut antenna (for VHF-LO channel 6) was modeled by 300ohm and found to provide great gain (9.17 dBi Raw Gain with a SWR of 1.82 at 85 MHz) while also featuring an extremely sharp cut off after channel 6 (which limits the effects of interference from low band FM Radio stations).

Question: are the photos, diagrams, and 4NEC2 info in this thread amount to enough for a DIYer to build one?

Also, does the design scale well for other VHF-LO channels or do we need to find the actual Delhi models for those channels?

 

[300ohm]

Question: are the photos, diagrams, and 4NEC2 info in this thread amount to enough for a DIYer to build one?

I certainly could, heh. Also the fact that all the elements, including the driven element , are electrically connected to the boom which is electrically connected to the mast, makes it even more goof proof and easier to build.

Also, does the design scale well for other VHF-LO channels or do we need to find the actual Delhi models for those channels?

Yes. I just did a simple channel 2 rescale of it and it seems to rescale well, with about the same gain and SWR numbers. The usable bandwidth is even narrower, but still plenty for one channel.

For channel 2, Its about a 3 meter boom and 2.7 meter total width reflector, using 15 mm diameter elements. So, the material price is going to be high.

 

[stampeder]

It's satisfying to know that for those who want to build a channel cut VHF-LO (single channel 2, 3, 4, 5, or 6) antenna this great Delhi design has not disappeared into oblivion, thanks to roger1818, jrmclean, and 300ohm.

 

[ScaryBob]

Good work gentlemen.

Wade/Taco still publishes specs for this line of antennas here.

They also list some commercial grade single channel yagis here. I inquired into their availability and received no response.

 

[stampeder]

I've attached that PDF file here to this post for our members in case it ever was to disappear from Wade's site.

The antennas in the Commercial-grade document are not of this original Delhi variety so I won't attach that file here. Apart from the Wade-Taco-Jerrold commercial antennas shown in there I believe some of them are originally from the old Lindsay brand of top quality CATV Head End antennas and gear that now belong to Wade.