New Antenna for Kerberos SDR

Discuss KerberosSDR - 4x Coherent RTL-SDR
arrowantennas
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New Antenna for Kerberos SDR

Post by arrowantennas » Tue Mar 24, 2020 11:23 pm

We have added a new antenna to our product line. It is specifically designed for KerberosSDR.

It can be found at http://arrowantennas.com/arrowii/sdr.html

I would like feedback on it from the community. I don't know what to do with the bottom of the mast to make mounting it easiest for users. We can drill holes through the mast, to mount it on the apex of a roof, but I am concerned that everyone's mounting situation would be different. I would love everyone's feedback. Also, we can make these with elements tuned as low as 52 MHz and as high as 500 MHz with appropriate spacing. What would the SDR community like?

I am also interested in putting more than one set of driven elements on one antenna. I would like feedback on this idea. We could make it with elements and holes to put them on the crossed booms but maybe only used one set on the booms at a time. Or possibly use more than 4 at a time with more than one KerberosSDR radio.

Lastly, what length of coaxial cables would be appropriate for this? I am thinking 10 to 15 feet with male BNC on one end and male SMA on the other.

Please email me at [email protected].
Thanks to everyone for looking and for your feedback.
Tim Chapman
Owner - Arrow Antennas.
www.arrowantennas.com

ckoval7
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Re: New Antenna for Kerberos SDR

Post by ckoval7 » Wed Mar 25, 2020 12:16 am

If you can do that with a second set of driven elements for 440 I would definitely pay ~$150 for it. As for the coax length, 25-30 ft would be better with connectors that are a bit more water tight than BNC. Definitely keep a tight tolerance on the coax lengths for each array.

rtlsdrblog
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Re: New Antenna for Kerberos SDR

Post by rtlsdrblog » Wed Mar 25, 2020 4:47 am

Very nice! Going to order some to test out. Dipoles definitely do work best, but it can be hard to use them on a roof of a car while in motion for example. But for a fixed site this will be perfect.

With the coax cables, just try to make sure that they are as equal length as possible.

I would definitely like to see different sized elements for different bands too.

arrowantennas
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Re: New Antenna for Kerberos SDR

Post by arrowantennas » Wed Mar 25, 2020 5:08 am

For mobile use, I would like to see someone try a mag mount with a 3/8" stud in the center like this one:
https://www.ebay.com/i/252565672116
A 3/8" bolt would go up the center of the bottom of the mast to hold the center in place.

Then guy the antenna a little out on each arm down to the car so it won't twist or move.
We will make cable sets as well which will be the same length.

I am working on a source for waterproof BNC connectors. It is my understanding that they exist. My supplier is looking for me.

Thanks to all for the feedback so far.
Tim.
Last edited by arrowantennas on Wed Mar 25, 2020 6:26 am, edited 1 time in total.

arrowantennas
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Re: New Antenna for Kerberos SDR

Post by arrowantennas » Wed Mar 25, 2020 6:25 am

I have also considered trying to make one set of antenna mast with cross booms that could cover a much wider range of frequencies. See my spreadsheet at www.arrowantennas.com/ksdr.xlsx.
Focus on the yellow part of the speadsheet please.

Our shipping boxes allow about 55 inches internal length. We can make booms and masts longer than that by splitting them as you see here: http://arrowantennas.com/arrowii/146-4ii.html
and on page 5 of this document: http://arrowantennas.com/inst/146437-10 ... _Sheet.pdf

Using +/- 20% as a guide for usable frequency of a dipole on these antennas for KerberosSDR, the yellow part of the spreadsheet with 7 driven element sets would achieve coverage of approximately 41 to 707 MHz. We would drill holes in the booms at the appropriate distances from center and split the booms in appropriate places to allow the different driven element sets to be used with minimal excess boom beyond them.

If you look at the non-yellow portion of the spreadsheet, you see that using 8 driven element sets, we could get coverage from 24 MHz up to 615 MHz. The problem with the low frequencies here is that our arrow shafts from which the dipoles are made are 30" long. We can screw them together as is done on this antenna: http://arrowantennas.com/arrowii/52-1.html

That can give us the 98" length required, but it would be very flimsy and I would not be comfortable manufacturing that. This is why the yellow part of the spreadsheet is more practical. Having not used the KerberosSDR yet, I don't know for sure, but assume that the movement of those flimsy elements in the slightest wind would make the signals received by the antennas differ and make them useless.

Note that we don't make antennas above 500 MHz normally because our manufacturing methods make tuning antennas above that a bit tricky.

Lastly, I will have BNC to SMA cables on our BNC Patch Cables page soon. So far, I am seeing interest in 15 and 25 foot sets. We will make them the same length so that the antennas work as well as possible.

For those of you who live outside the US, to get shipping amounts from our website, add the items to your cart. Proceed to checkout. Before you finalize checkout, you will see the shipping amount. We don't have any other way to get you a shipping quote.

Again, I am open to suggestions and questions.

Tim Chapman
Owner - Arrow Antennas
www.arrowantennas.com

ckoval7
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Re: New Antenna for Kerberos SDR

Post by ckoval7 » Wed Mar 25, 2020 10:59 am

arrowantennas wrote:
Wed Mar 25, 2020 5:08 am
I am working on a source for waterproof BNC connectors. It is my understanding that they exist. My supplier is looking for me.
If you have to look that hard for them, they'll probably be more expensive than going with a threaded connector.

arrowantennas
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Re: New Antenna for Kerberos SDR

Post by arrowantennas » Thu Mar 26, 2020 12:34 am

The BNC male connectors have a gasket to seal them. We will seal the coax with silicone. Further sealing can be done by the customer as is required on all RF connectors on antennas.

auroran
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Re: New Antenna for Kerberos SDR

Post by auroran » Fri Mar 27, 2020 8:47 pm

I know for myself I'll want a set that's optimized for the aircraft ELT frequency of 121.5 MHz .
Several of my associates in search and rescue may want that as well.

arrowantennas
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Re: New Antenna for Kerberos SDR

Post by arrowantennas » Fri Mar 27, 2020 9:25 pm

Would you also want that same antenna to have elements for 243.0 MHz and 406 MHz?

auroran
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Re: New Antenna for Kerberos SDR

Post by auroran » Sat Mar 28, 2020 6:48 pm

full tri-band would be awesome.

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