Ant. And Balun Questions For High Z Input, Please

Useful information regarding antennas for SDR products.
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Robert11
Posts: 81
Joined: Fri Sep 28, 2018 12:00 pm

Ant. And Balun Questions For High Z Input, Please

Post by Robert11 » Wed Oct 17, 2018 12:50 pm

Hi Folks,

Sr. Citizen dumb question:

Have a new RSP-2

Present setup is a long wire outside the house, which feeds a Balun at its end, and then a
fairly long run of coax into the house and ANT A.

Work pretty well. I listen most anywhere from 30 MHz and down.

Do you think it would make sense to take the coax off of the ANT A input, buy, e.g., that Noo Elec 9:1 Balun,
use it on the house coax end side, and take the
Balun output into the High Z input ?

Thought I would ask here first before buying the Noo Elec Balun.

In a way, it seems perhaps questionable to have a Balun outside from the long wire to the coax, and then another one inside the house from the coax end to the High Z input. Two Balun's ?

High Z input really "significantly" better than the ANT A input ?

Any thoughts and certainly suggestions would be most appreciated.

Thanks,
Bob

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Roger
Posts: 217
Joined: Fri Dec 29, 2017 7:59 pm

Re: Ant. And Balun Questions For High Z Input, Please

Post by Roger » Wed Oct 17, 2018 5:56 pm

Bob,

Here is a comment from RSP Tech support about the HiZ vs AntA ports on HF.
Use of HiZ vs AntA on RSP2.PNG
Use of HiZ vs AntA on RSP2.PNG (30.97 KiB) Viewed 21443 times
I have a couple of the NooElec baluns. They work quite well on the Hi-Z port and although not designed for LF (below 500 kHz) they do work OK. If you are an LF enthusiast you could wind your own balun using a Mix 73 toroid. Here is an app note from SDRPlay on using the HiZ port on the RSP2 >> http://www.sdrplay.com/wp-content/uploa ... uidev2.pdf

Roger

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Robert11
Posts: 81
Joined: Fri Sep 28, 2018 12:00 pm

Re: Ant. And Balun Questions For High Z Input, Please

Post by Robert11 » Wed Oct 17, 2018 7:12 pm

Hi,

Confused a bit over the statement:
"The High Z Port only has a low pass response"

So, below about 1.5 MHz, the use of Ant A and Ant B inputs are NOT recommended.

Fine, below 1.5 MHz it should be the High Z.
But, might someone clarify the following for me:

a. Below 1.5 MHz I want to use the high Z True ?

b. Above 1.5 MHz do I still want to use the High Z input ?

Can someone please divide up the range up to 30 MHz, and what Ant inputs are best, where ?

c. And, what about above 30 MHz: what's best, where ?

d. And for the vhf/uhf ranges ?

This should probably be good info for a lot of non-antenna folks like me.

Thanks,
Bob

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Roger
Posts: 217
Joined: Fri Dec 29, 2017 7:59 pm

Re: Ant. And Balun Questions For High Z Input, Please

Post by Roger » Thu Oct 18, 2018 12:03 am

Robert11 wrote: Confused a bit over the statement:
"The High Z Port only has a low pass response"
This means it passes all signals below 30 MHz. and not above that frequency.
So, below about 1.5 MHz, the use of Ant A and Ant B inputs are NOT recommended.

Fine, below 1.5 MHz it should be the High Z.
But, might someone clarify the following for me:

a. Below 1.5 MHz I want to use the high Z True ?
Yes the HiZ will give the best performance for MW, LF and VLF.
b. Above 1.5 MHz do I still want to use the High Z input ?
Can someone please divide up the range up to 30 MHz, and what Ant inputs are best, where ?
SDRplay reports that the HiZ is the best option for HF up to 30 MHz. However I have found that above 5 MHz. the performance of Ant A is very good and you don't need a balun. You also need to use Ant A/B for 1.8 to 30 MHz if you are near strong MW stations because it has a MW band rejection filter (the HiZ does not). The Ant A/B ports also has a 12 MHz. low pass filter which reduces spurious signals ("ghosts") that sometimes occur below 10 MHz. due to what is known as high-order mixing in the RSP.
c. And, what about above 30 MHz: what's best, where ?
d. And for the vhf/uhf ranges ?
Above 30 MHz. you can only use Ant A or B because the HiZ stops at 30 MHz.
Ant B has slightly worse performance because of the Bias-T circuitry.

Roger

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Mike2459
Posts: 318
Joined: Mon Jul 24, 2017 8:24 pm

Re: Ant. And Balun Questions For High Z Input, Please

Post by Mike2459 » Thu Oct 18, 2018 4:09 am

Hi-Z Port
22 megs Hi-Zt.JPG
22 megs Hi-Zt.JPG (189.1 KiB) Viewed 21402 times
It's nearly midnight, sunspots are at/near a minimum, one would expect 22 mhz would be dead at this hour. In fact it is. The Hi-Z port is mixing the AM broadcast band (530-1700khz)

FYI 22565 is WBZ in Boston.

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Roger
Posts: 217
Joined: Fri Dec 29, 2017 7:59 pm

Re: Ant. And Balun Questions For High Z Input, Please

Post by Roger » Sat Oct 20, 2018 2:54 am

Mike2459 wrote:Hi-Z Port
22 megs Hi-Zt.JPG

It's nearly midnight, sunspots are at/near a minimum, one would expect 22 mhz would be dead at this hour. In fact it is. The Hi-Z port is mixing the AM broadcast band (530-1700khz)

FYI 22565 is WBZ in Boston.
What you are seeing is high order mixing and it generates spurious signals ("ghosts"). This happens in any radio that employs an analog mixer circuit; traditional analog or tuner-based SDR (like the RSP). The problem gets worse the wider the received bandwidth because the front-end of the receiver has very wide RF filters. . Conventional analog HF receivers are narrowband (5 to 20 KHz. IF) and are triple conversion designs in order to reduce spurious signals. They also have tracking RF band filters on the receiver front-end. The RSP is a wideband receiver with a bandwidth up to 10 MHz. and so the performance will suffer because of the high bandwidth. Several things can be done to alleviate the situation. One method is to engage the notch filters like the MW or FM ones on the RSP1A, RSP2 (Ant A/B ports only) or RSPduo (all ports). The second is to change the LO frequency. The third is to switch from Zero IF to Low IF or vice versa. The fourth is to purchase a pre-selector that can be tuned for the band of interest thereby reducing the level of out-of-band signals.

Users that wish to avoid high order mixing entirely will have to purchase a direct sampling receiver. These directly digitize the entire HF spectrum from 0 to 30 MHz. and do not not use a tuner (no analog mixers). However they are more costly and for hobbyist applications do not receive higher that 60 MHz. unless a mixer is used to down-convert the higher frequencies.

For more information on high order mixing see this application note by SDRplay...
https://www.sdrplay.com/docs/SDRplay_Op ... _MW_HF.pdf

Roger

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Mike2459
Posts: 318
Joined: Mon Jul 24, 2017 8:24 pm

Re: Ant. And Balun Questions For High Z Input, Please

Post by Mike2459 » Sat Oct 20, 2018 5:05 am

Thanks Roger
I was being facetious. Seems, I've been spoiled by the old Collins R390A/URR :)

Mike

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