The Toronto VHF Society plans to use the 46-meter (150') dish at the Algonquin Radio Observatory (courtesy of the Institute for Space and Terrestrial Science, York University) during the 1995 A.R.R.L. International E.M.E. Competition. We will operate both weekends of the contest and plan to activate the 50, 144, 222, 432, and 1296 MHz bands during this time.
Recently, several people have inquired about the minimum station equipment required to make a QSO. Below are some estimates based on standard link-budget calculations.
The VE3ONT dish has the following approximate gain figures:
Table 1 ---------------------------------------------------------------- Frequency Theoretical Actual Actual MHz gain, dbi gain, dbic gain, dbil ----------------------------------------------------------------- 50 25.0(l) 25.0(l) 25.0 44 34.2(c) 34.2 31.2 222 37.9(c) 37.5 34.5 432 43.7(c) 43.1 40.1 1296 53.3(c) 52.0 49.0 -----------------------------------------------------------------
Interpreting Table 1: "Theoretical Gain" represents calculated gain based solely on dish diameter and operating frequency. "Actual Gain" represents our best estimate of how much gain VE3ONT really develops. For example, our 1296 MHz feed under-illuminates the dish by a few percent, resulting in approximately 1.3 dB reduction in gain. "dbic" indicates that the gain figures are relative to circularly polarized signals; except on 50 MHz, VE3ONT uses circular polarization. "dbil" represents gain relative to a linearly polarized antenna. To compute "dbil" from "dbic" we just subtracted 3 dB for circular/linear loss. If you are using an OSCAR-class circular-polarized antenna, you should refer to the "dbic" column whereas linearly-polarized antennas relate to the "dbil" column.
----------------------------------------------------------------- Table 2 Antenna Gain Required to Barely Hear VE3ONT ------------------------------------------------------------------ Frequency Antenna gain required MHz dbi dbd ------------------------------------------------------------------ 50 19 17 144 12 10 222 10 8 432 7 5 1296 15 13 ------------------------------------------------------------------
Interpreting Table 2: These figures are based on VE3ONT transmitting full legal power on 50 - 432 MHz and 200 watts on 1296. They also assume that the receiving antenna is polarized similarly to VE3ONT's signal. Note that this means linear polarization on 50 MHz and RHCP on the other bands. If your receiving antenna is polarized differently (for example, if you use a linear-polarized antennas on 144 MHz) then you will need about 3 dB more gain for the same received signal. Lastly, Table 2 assumes a receiver noise figure of about 0.5 dB. If you have no low-noise preamplifier, or if your preamp is located in the shack rather than at the antenna, you will need more antenna gain to compensate for the increased noise figure.
If you want to work VE3ONT via EME, you will also need to be loud enough at VE3ONT for us to hear you. If you can transmit the same power that VE3ONT is transmitting, then we ought to hear you about as well as you hear us. If you run less power, then you will need more antenna gain to make up for it. For example, if you transmit 150 watts on, say, 432 MHz instead of 1,500 watts, then you will need about 10 dB more antenna gain than Table 2 lists in order for VE3ONT to hear you.
Table 2 shows that the 432 MHz band is probably the most promising band for most people. The antenna gain required is reasonable and generating a moderate amount of transmit power is not too difficult. The 50 MHz band will be a significant challenge because of the large antennas and high power needed. However, "ground gain" may add up to 4-6 dB for a short period as the Moon nears your horizon.
Experience during the past 3 years has shown us that QRM, not signal strength, is often a limiting factor. We have recorded 20 stations calling within a 1.3 kHz bandwidth at one time. Obviously, weaker stations are difficult to copy even if they are strong enough to be detected. Consequently we recommend that all stations, especially weaker ones, spread out and call VE3ONT throughout the 10 kHz receive windows listed below (5 kHz on 50 MHz). We really do tune the full window. In fact, we tend to stay away from our own TX frequency because our own EME echoes are deafening.
To work VE3ONT on 144, 222, or 432 MHz, you'll need about 100 watts, a long-boom yagi, and patience. The more that you have of any of these three components, the better your chances. We hope you make it!
Repeated below is the proposed operating schedule for VE3ONT in 1995. It is identical to the schedule posted on 8/24/95.
------------------------------------------------------------------------- Band Date Time VE3ONT TX VE3ONT RX (UTC) (UTC) frequency freq. window ----------------------------------------------------------------------- 144 MHz Oct 6/7 0000-0910 144.100 144.100-144.110 50 & Oct 7/8 2305-1020 50.100 50.100 -50.105 1296 MHz 1296.050 1296.050-1296.060 222 MHz Oct 8/9 2335-1120(*) 222.010 222.010-222.020 432 MHz Nov 3/4 0000-0805 432.050 432.050-432.060 144 MHz Nov 4/5 2135-0910 144.100 144.100-144.110 144 MHz Nov 5 2205-2400 144.100 144.100-144.110 --------------------------------------------------------------
(*) 222 MHz: Only 2335-2400 UTC QSOs count for the EME contest; VE3ONT will be active all night anyway
Notes:
1) VE3ONT will attempt to be on the air at moonrise prior to the start of both the October and November weekends. We encourage only those who have not yet worked an EME station to try working us at that time. Experienced EME operators, please wait until the start of the contest. Anyone who works VE3ONT before the contest is encouraged to work us again during the contest.
2) Please avoid multiple QSOs during the contest. They only detract from the opportunity of first-time EME stations. If you wish to work VE3ONT on SSB, wait until we switch; don't work us first on CW and then repeat on SSB, please. Also, please avoid duplicate 144 MHz QSOs between the two weekends.
3) The 50 MHz and 1296 MHz operation scheduled for October 7/8 will be simultaneous on both bands, barring unforeseen difficulties.
4) As always, VE3ONT's operation is subject to last-minute cancellation for commercial users of the site.
5) In order to maximize your chances of making a QSO, make use of the entire receive window. Our best weak-signal successes in previous years have been well away from our TX frequency. We tune the window constantly.
6) Times shown reflect the dish's 9 degree lower elevation limit, not actual moonrise at the site (grid FN05xw).
7) 50 MHz will use horizontal polarization. 144, 222, and 432 MHz will be RHCP on both TX & RX in order to minimize Faraday/spatial polarization effects. Your linearly polarized or circularly polarized OSCAR antenna will work fine. 1296 will be switchable RHCP/LHCP for both TX & RX; default is RHCP.
8) VE3ONT will transmit maximum legal power on 50, 144, 222, and 432 MHz. 1296 MHz power will be at least 150 watts.
9) We expect 222 MHz activity to be concentrated near horizon times. Be aware that we are limited to +9 degrees elevation lower limit. Therefore stations on the North American East Coast will have to elevate their antennas to work us on 222 MHz. We encourage very small stations to try because QRM will be minimal and we will be on the air all night even though this is after the contest.
10) All operation will be "random," that is, without prearranged skeds.
11) QSLs go to Dennis Mungham, VE3ASO, RR #3, Mountain, Ontario, Canada, K0E 1S0. Inquiries to Peter Shilton, VE3VD, 215 Windecker Rd. R.R. #1, Cayuga, Ontario, Canada N0A 1E0 or call (905) 772-8938 (EDT/EST evenings).
For Comments or More Info, contact: W9IP. ( 9/25/95)
For your comments: W6/PA0ZN.
