A diplexer allows two different devices to share a common communications channel. Typically, the channel is a long coaxial cable, and a diplexer is often used at both ends of the coaxial cable. The plan is feasible if the two devices operate on different frequencies. The plan is economical if the diplexers cost less than running a second cable.
Diplexers are typically used with radio receivers or transmitters on different, widely separated, frequency bands. A single city radio tower might have a police department antenna on 460 MHz and a fire department antenna on 156 MHz. A diplexer at the top combines the two antenna signals to the single coaxial feedline, and a second identical diplexer inside the building separates the feedline signals to the two dispatch radios. Some diplexers support as many as four antennas or radios that work on different radio bands.
Diplexers are also commonly used where a multi-band antenna is used on a tower, with a common feedline. The diplexer will split the two bands inside the building (such as VHF and UHF systems combined with a diplexer onto a common antenna).
Martin,
a diplexer is a device to feed one antenna from two transcievers, since it
splits signals according to their frequencies.
https://en.wikipedia.org/wiki/Diplexer
you might be thinking of a splitter.
John, i have a really nice 2.4GHz directional coupler by Narda, it has four
ports unlike the slightly similar one in this picture:
http://www.recycledgoods.com/media/catalog/product/cache/1/i mage/1000x/af097278c5db4767b0f e9bb92fe21690/n/a/narda- microwave-corp.-3002-30- coaxial-directional-coupler-2. 0-ghz-1.27.jpg
you can borrrow it if you want, I also have attenuators and stuff like that.
-jake
On Thu, 3 Nov 2016, Martin wrote:
John,
The coupler you got is probably a diplexer - a device to feed two antennas
with one cable.
To do the testing that you're thinking of requires a directional coupler
like this: http://www.ebay.com/itm/Mini-Circuits-Coaxial-RF-Direc
tional-Coupler-ZADC-13-2000-1-13dB-SMA-50-Ohm-NEW-/291379146
740?hash=item43d78ceff4:g:A0IAAOSwqu9U2rgN The seller claims that the
units were tested to 2800 MHz and worked. This is a pretty good deal.
For the noise source you can use one of these: http://www.ebay.com/itm
/DC-12V-0-3A-SMA-noise-source-Simple-spectrum-external-
tracking-source-DY2-/172150915301?hash=item2814fe80e5:g: OaUAAOSwI3RW-t7N
You don't need a spectrum analyzer - a Hack-RF or similar SDR will do.
Connect the noise source to the directional coupler input and the antenna
to the coupler output. Attach the SDR to the coupler's coupled port. With
your favorite SDR software tune your radio to mid-band (2.442 - 2.447
GHz). Note the receiver power level. Reverse the antenna and noise
source, repeat measurement. The larger number is the power delivered to
the antenna, the smaller is power reflected back from the antenna. You can
use an online calculator like this http://rfcalculator.mobi/
vswr-forward-reverse-power.html to calculate VSWR. The ideal VSWR is one
and an antenna with greater than three should not be used.
Although the antennas are only rated to 2.2 GHz they may be usable at 2.4
GHz. Check the VSWR.
The antennas are probably useful for hams (there's a 902.005 MHz through
927.995 MHz band). I can ask around and see if there's is any interest.
You might want to put one one ebay and see if there's a market.
--Martin
On Thu, Nov 3, 2016 at 1:14 PM, John Fitz <johnfitzeecs@gmail.com> wrote:
Dang, well I picked up the pallet of antennas and it looks like they're
the CELLMAX-EXT-CPU which only cover 806–960 MHz and 1710–2200 MHz :( .
Hey but on the plus side, they contain tee couplers that are rated for the
full 698–960 MHz and 1710–2700 MHz. I've needed a 2.4Ghz coupler for a
while now and that alone was worth the minimum bid for me. With one of
those, a noise source and a spectrum analyzer, I can start characterizing
Wifi/Bluetooth antennas.
The antenna design is relatively simple and pretty cool looking. It would
be interesting to try and simulate the design and see how much would have
to change in order to extend the range. Also, if anyone wants to build a
phase arrayed radar system...
On Fri, Oct 28, 2016 at 6:57 PM, Marc Juul <juul@labitat.dk> wrote:
Are you sure these cover 2.4 GHz. There are multiple versions of the
CELLMAX-EXT and e.g. the CELLMAX-EXT-CPU seems to not cover 2.4 GHz while
the CELLMAX-EXT-CPUSE does cover 2.4 GHz:
http://www.commscope.com/catalog/wireless/product_details. aspx?id=151
https://www.tessco.com/products/displayProductInfo.do?sku= 396652
if we're sure they cover 2.4 GHz then we'd love to get them! I'd pay up
to $100 in that case
On Fri, Oct 28, 2016 at 4:55 PM, Jake <jake@spaz.org> wrote:
pallet of high gain (11dbi) directional wifi antenna's up for auction:
https://www.auctionbdi.com/listings/details/index.cfm?itemnu m=1158888078
Fitz says they can probably be won for $25 and i think he's willing to
bid on them for sudomesh
so if sudomesh wants them, they should tell Fitz how much Sudomesh will
pay for the lot. 140 pounds of antennas.
Fitz, did you have a datasheet on these antennas? I believe i recall
they were wideband in the 900MHz and 2.4GHz bands?
-jake
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