{"id":63,"date":"2019-04-19T15:30:59","date_gmt":"2019-04-19T15:30:59","guid":{"rendered":"https:\/\/fletch.scot\/wp\/?p=63"},"modified":"2020-08-29T16:01:18","modified_gmt":"2020-08-29T16:01:18","slug":"sdrplay-safety","status":"publish","type":"post","link":"https:\/\/fletch.scot\/wp\/?p=63","title":{"rendered":"SDRplay Safety"},"content":{"rendered":"<p>\u00a0<\/p>\n<p>I bought an <a href=\"https:\/\/www.sdrplay.com\/rsp2\/\">SDRplay RSP2 SDR<\/a> recently. I had been looking for a multimode VHF\/UHF transceiver but couldn\u2019t find one within my budget. The transceivers that get listed on eBay go for silly prices and I\u2019m not sure I want to pay the asking price for a new model.\u00a0<\/p>\n<p><img decoding=\"async\" title=\"\" src=\"https:\/\/www.sdrplay.com\/wp-content\/uploads\/2016\/11\/RSP2.png\" alt=\"\" width=\"\" height=\"\" border=\"0\" \/><\/p>\n<p>So I\u2019ve decided to concentrate on receiving signals from satellites rather than transmitting, hence the purchase of the RSP2.<\/p>\n<p>One of the specs of the RSP2 is the maximum signal it will tolerate at its aerial inputs. It says 0dBm which by my calculations says the voltage at the input must\u00a0be under 0.22 Vrms to be safe. This sent alarm bells ringing as my Cebik Moxon aerials share the same attic as my small transmit loop aerial.<\/p>\n<p>So I made some measurements.<\/p>\n<p>I measured the voltage seen in the shack from the Cebik Moxons when transmitting 10W to the magnetic loop. The measurements were on my <a href=\"https:\/\/www.keysight.com\/main\/techSupport.jspx?cc=US&amp;lc=eng&amp;nid=-32416.536881905&amp;pid=1000001432%3Aepsg%3Apro&amp;pageMode=OV\">HP 54615B scope<\/a> with a 50\u03a9 termination.<\/p>\n<p>No RF 800\u00b5V<br \/>TS590S tune (10W) 191mV at 14.2 MHz <br \/>TS590S tune (10W) 288mV at 7.07 MHz<\/p>\n<p>So my RSP2 is unsafe in its current location and configuration. I must not transmit using my HF rig if I have the RSP2 connected to my Cebik Moxon aerials.<\/p>\n<p>My first thought was to put a high pass filter on the Cebik Moxons to block 6m and below. I\u2019m sure this would work but there would be some insertion loss.<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/images.shopwired.co.uk\/images\/user\/fileUp\/radioworld2\/m-100.jpg\" \/><\/p>\n<p>But I have an Moonraker M-100 masthead preamp which has a 24-2300 MHz filter. This wouldn\u2019t block 10m and 6m, but I don\u2019t transmit on those bands using the small transmit loop and if I did the radiated power would be quite small as the impedance mismatch would be high.<\/p>\n<p>So I made some more measurements with the M-100 in the shack. I know these won\u2019t give the same effective gain at the receiver as measurements made with the M-100 in the attic, but it\u2019s close enough for a start. The dial on the M-100 is laughable as the gain you get at each position bears only a passing relationship to the actual gain. The most you can say is the more clockwise the dial the higher the gain. Hence the \u2018on dial\u2019 below.<\/p>\n<p>\u2022 Zero gain (on dial)<br \/>No RF 18mV<br \/>10W 14.2MHz 32mV<br \/>10W 7.07MHz 39mV<\/p>\n<p>\u2022 gain +10 (on dial)<br \/>No RF 18mV<br \/>10W 14.2MHz 25mV<br \/>10W 7.07MHz 53mV<\/p>\n<p>\u2022 gain +20 (on dial)<br \/>No RF 19mV<br \/>10W 14.2MHz 559mV<br \/>10W 7.07MHz fuzzy on the scope so I assume the signal is distorted somehow<\/p>\n<p>\u2022 gain at 12 o\u2019clock<br \/>No RF 18mV<br \/>10W 14.2MHz 50mV<br \/>10W 7.07MHz 16mV<\/p>\n<p>This looks promising as the preamp gain should be set to just retrieve the loss from the cable and this should end up being 12 o\u2019clock or lower.<\/p>\n<p>The next step is to install the M-100 in the attic and re-measure. I\u2019ll probably use a bias-tee arrangement so I can power it from the shack.<\/p>\n<p>\u00a0<\/p>\n<p>\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u00a0 I bought an SDRplay RSP2 SDR recently. I had been looking for a multimode VHF\/UHF transceiver but couldn\u2019t find one within my budget. The transceivers that get listed on eBay go for silly prices and I\u2019m not sure I want to pay the asking price for a new model.\u00a0 So I\u2019ve decided to concentrate &hellip; <\/p>\n<p class=\"link-more\"><a href=\"https:\/\/fletch.scot\/wp\/?p=63\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> &#8220;SDRplay Safety&#8221;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[12,26],"tags":[34,32,35],"class_list":["post-63","post","type-post","status-publish","format-standard","hentry","category-radio","category-space","tag-radio","tag-satellite","tag-sdr"],"_links":{"self":[{"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=\/wp\/v2\/posts\/63","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=63"}],"version-history":[{"count":1,"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=\/wp\/v2\/posts\/63\/revisions"}],"predecessor-version":[{"id":64,"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=\/wp\/v2\/posts\/63\/revisions\/64"}],"wp:attachment":[{"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=63"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=63"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=63"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}