Derek, We only have to hit 18V/m during calibration so we were told we only need a 50 watt amp between 1Ghz and 4.2Ghz and a 35 watt amp between 4.2Ghz and 6Ghz, so fairly low power.
If we locate the amp in the chamber near the horn we can hit our calibration numbers with a 6 foot long RG393 cable between the amp and the horn. We are contemplating locating the amp(s) and all the supporting test equipment in the chamber just as you suggest. We are testing in a 10 meter chamber that is also used for Emissions testing so we are continuously switching test setups between emissions and immunity. We are finding the test setup for high frequency radiated immunity to be so particular, especially with coax cable connections, we are starting to doubt if a reliable convertible setup can be achieved. As you are doing, we are considering mounting all the equipment in a rack and mounting it to the antenna mast so we do not have to connect and disconnect any coax cables. This would really improve the reliability of the setup. Locating the test equipment (and amps) outside the chamber requires us to use a 7 foot flexible cable between the antenna and the chamber floor (this is the cable I'm trying to select). We have a 35 foot LDF5-50A Heliax cable under the floor to our chamber bulkhead. Then we have a 6 foot 1/2" semi-rigid low loss cable to our AR Switchbox, then a 2 foot cable to the amps, all with "N-Male" connectors. I will also need a host of cables to connect the power meter probes and signal generator in and out of the AR switch box to the BDCs and amps, but these cables are all fairly short and low power. So that is our full setup. Not to highjack my own thread of finding a good affordable flexible low loss cable, but if anyone wants to comment or make suggestions on the rest of our test setup, please do. The Other Brian From: Derek Walton [mailto:[email protected]] Sent: Wednesday, July 16, 2008 1:29 PM To: Kunde, Brian Cc: Grace Lin; [email protected] Subject: Re: Low Loss Coax Cable Hi Brian, just something for you to think about. I faced the same problem in my lab when starting out testing at 200 v/m. We have since pushed this quite a bit higher and implemented a few things to get these higher levels: First, it's relatively easy to make up cable losses at low signal levels, and good shielded cables are easy to find. However, I had a cable run of about 20 feet to get to the antenna and through the room wall. I found the bulkheads and even the cable would get warm during testing. Also there were several notches in the drive level from the sig gen that should not really be there. So my first step was to move the high frequency amps ( 8 to 18 GHz ) inside the room. To start with I used a sucoflex cable to feed the signal in to the rack we had these in. That works well, but it''s ungainly. So I bought an optical GP-IB link and moved both the signal source and the power meter into the chamber too. All this resides in a low height rack on LARGE wheels, the TWT's are very heavy. I used a short length of Flexible Waveguide to hook up the horn, it's long enough to change polarity. We are in the process of doing this with the 1 to 8 GHz Amps, the cable will only be a few feet long. Using all horns for transmitting, I've not observed significant influence of the racks located behind the antenna. Sincerely, Derek Walton L F Research Kunde, Brian wrote: > > How would you rank the flexibility of the following cables? (so I an > get a comparison) > > *CABLE TYPE (Insertion Loss per ft at 10Ghz)* > > * * > > UFB311A (.15) > > LMR 600 (.17) > > LMR 400 (.27) > > UFA210A (.27) > > Gore PhaseFlex (.27) > > RG-214 (.47) > > RG-393 (.35) > > EM40 (.36) > > The UFB cable has the best insertion loss of the bunch but it is very > expensive. LMR 400 cables are cheap but I've never seen any so I don't > know if they are flexible. I have RG-214 cable and I find it ok to > work with so a comparison to RG214 would be good. I would guess that > LMR 600 is a tow rope. The UFA210A cable has similar loss compared to > LMR 400 but only half the diameter, so I guess much more flexible. > > I cannot get the Micro-Coax website Cable Wizard to work. When I get > to the part where I select a cable, I get a Server Error. So I have > not been able to see any prices for their cable assemblies. > > What other cable types/sources should I be looking at? > > Thanks to all for your help. I know this can seem like a very small > issue but I have no experience with high frequency low loss cable. A > fraction of a db can make a huge difference in our application > (radiated immunity up to 6Ghz) so I'm really dancing a line between > insertion loss vs flexibility. > > The other Brian > > > > *From:* [email protected] [mailto:[email protected]] *On Behalf Of > *Grace Lin > *Sent:* Wednesday, July 16, 2008 7:23 AM > *To:* [email protected] > *Subject:* Re: Low Loss Coax Cable > > Hi Brian, > > MegaPhase carries low loss cables > (http://www.megaphase.com/test06.html). Several commercial labs in the > northeast of the US use its cable. Order "EM40" for flexibility even > you don't need performance up to 40GHz. EM18 is not flexible and too > difficult to connect to instrument. > > The person who performed our NSA uses cables made by Micro-coax > (http://www.micro-coax.com/). From this link, > https://www.micro-coax.com/secure/(wk1c1ujm3fbhqjfmk2qho3fg)/MCConfigura tor.aspx > <https://www.micro-coax.com/secure/%28wk1c1ujm3fbhqjfmk2qho3fg%29/MCConf igurator.aspx>, > click "Select Cable Type", you will find informaiton for diffierent > cable types. The diameters of 0.14" and 0.205" are flexible. I have > UFB311A (not as flexible as I like) and UFB142A (flexible) with 12" > length. > > My colleague ordered a PHASEFLEX cable from W.L.Gore > (http://www.gore.com/en_xx/products/cables/microwave/test/gore_phaseflex _microwave_test_assemblies.html). > It is very flexible and durable. W.L.Gore provides online purchase and > can be received next day > (http://consumer.gore.com/webapp/wcs/stores/servlet/ProductDisplay?catal ogId=10401&storeId=10401&productId=10854&langId=-1&parent_category_rn=10 101 > <http://consumer.gore.com/webapp/wcs/stores/servlet/ProductDisplay?catal ogId=10401&storeId=10401&productId=10854&langId=-1&parent_category_rn=10 101>). > > The price range for the above mentioned cables is $300-$1000. > > Regards, > > Grace > > On 7/15/08, *Kunde, Brian* <[email protected] > <mailto:[email protected]>> wrote: > > What coax cable types do you recommend for a very low loss cable up to > 6Ghz but also flexible? I need a good low loss cable to connect > between my horn antenna and the floor connection of my Heliax. The > cable only needs to be 5 or 6 feet long but flexible enough so I can > change polarization on my antenna. > > I have looked at many cable types in catalogs and on-line but you > cannot tell if it will be flexible without seeing it for real. I > ordered a cable called "Helical Super Flex". I liked the low loss > properties but it was not at all flexible, let alone super flexible. > It was barely semi-rigid in my book . > > I tried RG393/U but it is not very flexible and I prefer a lower loss > cable if possible. > > What do you all recommend? What is the best? Where can I buy it in > small quantities and possibly in custom lengths? > > Thanks to all in advance. > > The Other Brian > > _________________________ > > *LECO Corporation Notice*: This communication may contain confidential > information intended for the named recipient(s) only. If you received > this by mistake, please destroy it and notify us of the error. Thank you. > > - ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering Society > emc-pstc discussion list. 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