Aha! AA Electronics & its next door store Sayal Electronics on Matheson Blvd E Mississauga are two of my favorite stores to get parts.
Please see below my drawing showing an example of amplifier setup. What you need is an amplifier, a power inserter, and a dc 15V power adapter. In case your antenna is dc shorted, you will need a dc blocker between amplifier & antenna.
Some Photos for Filter Lovers
Source: Richard Lee of Planefinder forum.
http://forum.planefinder.net/threads/ads-b-diy-antenna.23/page-13#post-745
https://farm8.staticflickr.com/7794/17225158090_023017a473_o.jpg
https://farm8.staticflickr.com/7733/17386451506_cb063cbf0b_o.jpg
https://farm9.staticflickr.com/8831/17224846180_6148bcf331_o.jpgu
All amplifiers will require power.
I see you are using 69 mm wire lengths. I know that lambda/4 is 68.8 mm, but a quarter-wave antenna is an electrical length specification, not a physical length.
For my own quarter-wave ground plane (bare copper 18 AWG wire at 1.09 GHz), I estimated and used 95% of lambda/4, or about 65.5 mm. It has been working very well.
I have tried to trim a halfwave dipole, and a Cantenna, starting at 69mm, and trimming 2mm at a time. I did not notice any difference between 69mm, 67mm & 65mm, but 63mm & 61mm were definitely inferior.
Here is photo of my actual system, with home-brew DC Power Inserter, and home-brew DC Blocker.
I have used one recycled 2-way TV Splitter as housing for DC Power Inserter, and another 2-way Splitter as housing for DC Blocker.
Cost:
One RCA D903 Amplifier from Sayal Electronics for $4 each
One 110V AC to 15 V DC power adapter from Sayal Electronics for $5.50
A pack of 2 pieces of 4.7 micro Henry Axial Inductor from Sayal Electronics for $1.50
Two numbers 200 pF ceramic disc Capacitor from AA-Electronics for $0.25 each
Two numbers 2-way TV splitter from a Dollar Shop for $1.50 each
This system was built two years ago, and is working perfectly well since then.
How would I find out if my antenna is shorted? It is a coaxial collinear.
dpdproductions.com/page_vhf_air.html#adsbout from DPD Productions. It’s the vertical base station antenna.
Also, for those of us who are not home brewers, do you know of a good option to purchase DC blockers if needed?
I would really like to give this a try.
Use an Ohmmeter to look for a short on the lead directly connected to the antenna. For example, my antenna is on the roof of my garage and a piece of RG6 coax runs from it down into the garage. If I wanted to check for a short I would connect my Ohmmeter between the centre conductor and the shield of the coax from the roof.
If you’re in doubt, use the DC Blocker anyway, it will not affect the circuit.
…Tom
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[size=150]DC VOLTAGE BLOCKER:
http://ebay.com/itm/370609430351
http://i.ebayimg.com/00/s/NDgwWDY0MA==/$(KGrHqR,!i!E9htEG3c9BPoBe1lzq!~~60_1.JPG
http://ebay.com/itm/251432963230
POWER INSERTER + 15V DC ADAPTER:
http://www.ebay.com/itm/221389012860
http://www.ebay.com/itm/221523231893
POWER INSERTER:
http://www.ebay.com/itm/371094073702
http://www.ebay.com/itm/131249139257
http://thumbs2.ebaystatic.com/d/l225/m/mszvklAs9pzTWRCv8FEUkMQ.jpg
http://www.ebay.com/itm/131506454888
http://thumbs1.ebaystatic.com/d/l225/m/mXTnpS54pnvTGgBHuK-DnpA.jpg
I built a power inserter for a different antenna system(radio astronomy), following the description at stargazing.net/david/radio/i … scope.html for the power supply. It’s not working at all, could anyone advise me on how to trace the power to see if the solders were good, and just where the item’s failing, and what tool(s) to use?
this text
[quote=“Itty Bitty Radio Telescope”]Power Supply box with two connectors
Radio Shack 273-0102 RF Choke, 100 microhenries
Blocks the RF from being shorted in the DC power source
Radio Shack 274-1582 Size M Panel-mount Coaxial Power Jack w/Switch
Radio Shack 278-0212 Panel-Mount F-61 Jack (2-Pack)
Radio Shack 270-1801 Project Enclosure (3x2x1")
The power for the Satellite Finder and the LNB is delivered by the RG6 coax. I made a small box Radio Shack 270-1801 Project Enclosure (3x2x1") with a F connector Radio Shack 278-0212 Panel-Mount F-61 Jack (2-Pack) and a M connector Radio Shack 274-1582 Size M Panel-mount Coaxial Power Jack w/Switch. DC power is connected to the M connector. The F connector is connected to the Satellite Finder to power it and the LNB. Inside the box the center of the M connector is connected to one end the Radio Shack 273-0102 RF Choke, 100 microhenries. The other end of the RF Choke is connected to the center of the F connector. The choke blocks the RF signal from the power source (two 9 volt batteries).
[/quote]
is complex to follow, but
Outer of F connector goes to the -ve of battery 1 (connect black probe of volt meter here)
+ve of battery 1 connects to -ve of battery 2 (red probe should be at 9v)
+ve of vattery 2 connects to choke (red probe should be at 18v)
Other end of choke connects to center of f-connector (red probe should still be at 18v)
Note: this does not provide the same function as the power injectors mentioned above since this has no function to pass a signal through the injector to the receiver. this signal passthru requires a second F connector and a 220pf capacitor.
Thanks for sharing, loads of good ideas here.
Looking to install a diplexer onto my 4 legged ground plane. Currently antenna has 6 feet of RG6 to the dongle. Do I need to add a power inserter as well? I see most people talking about diplexer’s using power inserters and DC blockers. Just want to make sure I wont be doing any harm.
The diplexer doesn’t require power so no power-inserter is required. I presume you want to use the diplexer as a filter?
A power-inserter is required when an inline pre-amp is used. And sometimes DC-blockers are required as well.
…Tom
Thanks for your response. Yes, I do want to use it as a filter. I will pop it on today and see how it goes.
Diplexers have insertion loss of 1 dB to 3.5 dB (depending on make & model), so you may notice some reduction in number of planes and maximum range.
https://farm9.staticflickr.com/8784/17119391833_c603b83f67_o.jpg
https://farm9.staticflickr.com/8863/17552185880_4f785375f6_o.jpg
https://farm8.staticflickr.com/7685/17739950651_8897578470_o.png
I posted response curves on a Holland splitter and an Eclipse splitter a while back.
the Eclipse part cuts off at around 906 MHz:
where the Holland doesn’t cut off until around 848 MHz:
The second take-away is that you don’t need fancy equipment (but it is nice to have) – you can do response plots like this based on your own environment using your SDR, and you should, if for no other reason than to know what you’re up against!
bob k6rtm
You can also use something like a zener diode noise source in conjunction with an RTL dongle to make a poor man’s analyser. It would probably be sufficient for testing basic filter characteristics - you won’t get very accurate levels from it, but you should be able to see the cut-off frequencies well enough.
This was posted in March. I’ve only just received all the bits I need. I had a go last night with coax stubs and it works. I’ll post pics when I understand what I’m doing.
http://www.rtl-sdr.com/rtl-sdr-tutorial-measuring-filter-characteristics-and-antenna-vswr-with-an-rtl-sdr-and-noise-source/
