I have a Hustler 5BTV antenna i resurrected after a previous monopole succumbed to birds.

It is giving me a world of trouble trying to get it tuned for resonance.

For those not familiar with the antenna its a 5-band trapped vertical.

It is ground-mounted (about 1 foot off the ground on a 1.5ft metal pole) with 8 radials below it (insulated electrical wire) running flat on the ground in each direction. 270-degrees is concrete underneath, and 90-degrees is dirt (garden bed).

Directly below the antenna on the pole is a home-made 1:1 choke (2 x FairRite FT240-31's w/11 turns of RG-400 around both toroids). An SO-239 on one side, and 2 bolts, one to centre element of the 5BTV via a 2" wire pigtail, and 1/2 foot wire pigtail to connect to radials below.

Transmission line is 32M of RG-213.

Below are the results from a NanoVNA (from nanovna-saver)

NanoVNA calibrated at feedpoint overlaid over NanoVNA calibrated at generator end (in blue) with 1:1 choke & 5BTV, RG-213:

And the same chart for the 1:1 choke with 2x100ohm wire-wound resistors in parallel replacing the antenna, VNA calibrated for load-end:

(grey bars are the ham bands from 160M)

I can get an acceptable tune on 80M (narrow-band as it's a coil), and 40M is ok on the low-side, but most other bands aren't usable (too high an SWR, mostly over 4:1 up to > 10:1).

I'm wondering if the SWR curve in the bottom-most image (choke) is what should be expected for 2xFT240-31's? Because the SWR of the choke rises on higher bands, i'm wondering if that's why i'm having trouble getting a tune on the higher bands?

Would appreciate any thoughts/insights..

I have a Hustler 5BTV antenna i resurrected after a previous monopole succumbed to birds.

It is giving me a world of trouble trying to get it tuned for resonance.

For those not familiar with the antenna its a 5-band trapped vertical.

It is ground-mounted (about 1 foot off the ground on a 1.5ft metal pole) with 8 radials below it (insulated electrical wire) running flat on the ground in each direction. 270-degrees is concrete underneath, and 90-degrees is dirt (garden bed).

Directly below the antenna on the pole is a home-made 1:1 choke (2 x FairRite FT240-31's w/11 turns of RG-400 around both toroids). An SO-239 on one side, and 2 bolts, one to centre element of the 5BTV via a 2" wire pigtail, and 1/2 foot wire pigtail to connect to radials below.

Transmission line is 32M of RG-213.

Below are the results from a NanoVNA (from nanovna-saver)

NanoVNA calibrated at load/feedpoint overlaid over NanoVNA calibrated at source/generator end (in blue) with 1:1 choke & 5BTV, RG-213:

And the same chart for the 1:1 choke with 2x100ohm wire-wound resistors in parallel replacing the antenna, VNA calibrated for load-end:

(grey bars are the ham bands from 160M-10M)

I can get an acceptable tune on 80M (narrow-band as it's a coil), and 40M is ok on the low-side, but most other bands aren't usable (too high an SWR, mostly over 4:1 up to > 10:1).

I'm wondering if the SWR curve in the bottom-most image (choke) is what should be expected for 2xFT240-31's? Because the SWR of the choke rises on higher bands, i'm wondering if that's why i'm having trouble getting a tune on the higher bands?

Would appreciate any thoughts/insights..

I have a Hustler 5BTV antenna i resurrected after a previous monopole succumbed to birds.

It is giving me a world of trouble trying to get it tuned for resonance.

For those not familiar with the antenna its a 5-band trapped vertical.

It is ground-mounted (about 1 foot off the ground on a 1.5ft metal pole) with 8 radials below it (insulated electrical wire) running flat on the ground in each direction. 270-degrees is concrete underneath, and 90-degrees is dirt (garden bed).

Directly below the antenna on the pole is a home-made 1:1 choke (2 x FairRite FT240-31's w/11 turns of RG-400 around both toroids). An SO-239 on one side, and 2 bolts, one to centre element of the 5BTV via a 2" wire pigtail, and 1/2 foot wire pigtail to connect to radials below.

Transmission line is 25M of RG-213.

Below are the results from a NanoVNA (from nanovna-saver)

NanoVNA calibrated at feedpoint overlaid over NanoVNA calibrated at generator end (in blue) with 1:1 choke & 5BTV, RG-213:

And the same chart for the 1:1 choke with 2x100ohm wire-wound resistors in parallel replacing the antenna, VNA calibrated for load-end:

(grey bars are the ham bands from 160M)

I can get an acceptable tune on 80M (narrow-band as it's a coil), and 40M is ok on the low-side, but most other bands aren't usable (too high an SWR, mostly over 4:1 up to > 10:1).

I'm wondering if the SWR curve in the bottom-most image (choke) is what should be expected for 2xFT240-31's? Because the SWR of the choke rises on higher bands, i'm wondering if that's why i'm having trouble getting a tune on the higher bands?

Would appreciate any thoughts/insights..

I have a Hustler 5BTV antenna i resurrected after a previous monopole succumbed to birds.

It is giving me a world of trouble trying to get it tuned for resonance.

For those not familiar with the antenna its a 5-band trapped vertical.

It is ground-mounted (about 1 foot off the ground on a 1.5ft metal pole) with 8 radials below it (insulated electrical wire) running flat on the ground in each direction. 270-degrees is concrete underneath, and 90-degrees is dirt (garden bed).

Directly below the antenna on the pole is a home-made 1:1 choke (2 x FairRite FT240-31's w/11 turns of RG-400 around both toroids). An SO-239 on one side, and 2 bolts, one to centre element of the 5BTV via a 2" wire pigtail, and 1/2 foot wire pigtail to connect to radials below.

Transmission line is 32M of RG-213.

Below are the results from a NanoVNA (from nanovna-saver)

NanoVNA calibrated at feedpoint overlaid over NanoVNA calibrated at generator end (in blue) with 1:1 choke & 5BTV, RG-213:

And the same chart for the 1:1 choke with 2x100ohm wire-wound resistors in parallel replacing the antenna, VNA calibrated for load-end:

(grey bars are the ham bands from 160M)

I can get an acceptable tune on 80M (narrow-band as it's a coil), and 40M is ok on the low-side, but most other bands aren't usable (too high an SWR, mostly over 4:1 up to > 10:1).

I'm wondering if the SWR curve in the bottom-most image (choke) is what should be expected for 2xFT240-31's? Because the SWR of the choke rises on higher bands, i'm wondering if that's why i'm having trouble getting a tune on the higher bands?

Would appreciate any thoughts/insights..